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Minimum flow rate required for unvented domestic hot water system
Many thanks to Andy Hall and others for their help earlier this year on the
design of my new plumbing system (http://tinyurl.com/3pwck etc.). Unfortunately, thanks to a few months illness, I'm still at it - with a few issues to resolve. A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? My feeling is that it isn't. At worst, I would guess that only one shower and the bath would be running concurrently. Even so, a power shower consumes 15 lpm and a bath consumes 20 lpm. Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... [For information, the hot water will be heated indirectly in a 250 litre tank by a condensing boiler. The mains supply pressure will be reduced (to 2 bar?) by a water softener, although a "high flow" softener, such as the Kinetico 2020c HF, will be fitted to minimise this problem.] Presumably the central heating could operate as a sealed system, even if the hot water tank is vented? TIA |
On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston"
wrote: Many thanks to Andy Hall and others for their help earlier this year on the design of my new plumbing system (http://tinyurl.com/3pwck etc.). Unfortunately, thanks to a few months illness, I'm still at it - with a few issues to resolve. A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? My feeling is that it isn't. At worst, I would guess that only one shower and the bath would be running concurrently. Even so, a power shower consumes 15 lpm and a bath consumes 20 lpm. I think that it's marginal. The static pressure is reasonable but not exciting. Flow rate isn't brilliant but not at a level where the supplier is likely to do anything for nothing. You could put flow restrictors on the feeds to the bath to protect the flow to the shower, and if you don't mind reasonable pressure but not high shower flow, you could do the shame with the showers and perhaps cut them to 10-12lpm. At these levels I think I'd try to do something about it. Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... Don't forget that there are tanks available in different shapes and sizes from Polytank and that one can always link more than one together if it helps with the nature of the space available. About the only other option is to look into having a larger diameter service pipe installed from the road main into the house. THis can be disruptive and not inexpensive of course. [For information, the hot water will be heated indirectly in a 250 litre tank by a condensing boiler. The mains supply pressure will be reduced (to 2 bar?) by a water softener, although a "high flow" softener, such as the Kinetico 2020c HF, will be fitted to minimise this problem.] Certainly a high flow type should be used.. Presumably the central heating could operate as a sealed system, even if the hot water tank is vented? Yes it can. TIA ..andy To email, substitute .nospam with .gl |
Andy Hall wrote in message ... On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston" wrote: snip Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... Don't forget that there are tanks available in different shapes and sizes from Polytank and that one can always link more than one together if it helps with the nature of the space available. About the only other option is to look into having a larger diameter service pipe installed from the road main into the house. THis can be disruptive and not inexpensive of course. Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". Space in my loft is very limited, but I do have basement space so I could get an accumulator. GAH make a "Dualstream" accumulator but you have to buy their rebadged Ariston unvented hot water cylinder with it. I don't know anything about the quality of Ariston. For a 300 litre accumulator and 300 litre cylinder the list price is £2112 (less 40% from a distributor I'm told!). The 300 litre accumulator is 5'2" high and almost 2' diameter so it takes up a lot of room. I suppose that I'll have to compare the Dualstream cost with a "cistern and pump" solution and take a view on it. |
(Sorry - Posted this reply using my wife's newsgroup reader by mistake...)
Andy Hall wrote in message ... On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston" wrote: snip Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... Don't forget that there are tanks available in different shapes and sizes from Polytank and that one can always link more than one together if it helps with the nature of the space available. About the only other option is to look into having a larger diameter service pipe installed from the road main into the house. THis can be disruptive and not inexpensive of course. Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". Space in my loft is very limited, but I do have basement space so I could get an accumulator. GAH make a "Dualstream" accumulator but you have to buy their rebadged Ariston unvented hot water cylinder with it. I don't know anything about the quality of Ariston. For a 300 litre accumulator and 300 litre cylinder the list price is £2112 (less 40% from a distributor I'm told!). The 300 litre accumulator is 5'2" high and almost 2' diameter so it takes up a lot of room. I suppose that I'll have to compare the Dualstream cost with a "cistern and pump" solution and take a view on it. |
"John Aston" wrote in message .. . (Sorry - Posted this reply using my wife's newsgroup reader by mistake...) Andy Hall wrote in message ... On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston" wrote: snip Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... Don't forget that there are tanks available in different shapes and sizes from Polytank and that one can always link more than one together if it helps with the nature of the space available. About the only other option is to look into having a larger diameter service pipe installed from the road main into the house. THis can be disruptive and not inexpensive of course. Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". Space in my loft is very limited, but I do have basement space so I could get an accumulator. GAH make a "Dualstream" accumulator but you have to buy their rebadged Ariston unvented hot water cylinder with it. I don't know anything about the quality of Ariston. For a 300 litre accumulator and 300 litre cylinder the list price is £2112 (less 40% from a distributor I'm told!). The 300 litre accumulator is 5'2" high and almost 2' diameter so it takes up a lot of room. I suppose that I'll have to compare the Dualstream cost with a "cistern and pump" solution and take a view on it. I assume you haven't bought any equipment yet. In your situation which I assume you have 1 bath and two showers, and I would go: 1. Combi boiler (to do the two showers only) 2. A "combination" cylinder with quick recovery coil. (cold tank and hot cylinder all in one space saving unit). This operates at low pressure http://www.rcmgroup.co.uk/specialized.htm RCM will make a large cold tank section for you. They will ake the hot and cold section sizes to order. The CH side of the combi acts as a normal system boiler heating the cylinder and CH. The cylinder does the bath and therest of the house to give good fillups. The water side of the combi only does high pressure showers. Something like an Alpha CB50, W-B Greenstar high flow condensing combi would do. The W-B Greenstar 40kW model can deliver 16 litres/min and you need to add cold to the showers, so a decent shower had if two on at the same time. This approach is cost effective and no power shower pump used. Another approach is a "combinatiuon" cylinder witha quick recovery coil serving all hot outlets and cold for showers using a conventional power shower pump for then showers and a condesning system boiler. Use a Torbeck ball valve in the cold section and 22mm cold mains directly to it to give repaid fills ups. The Torbeck is either on or off. Will you really have the bath filling and a shower on at the same time? A relative has had a single shower power shower pump serving two showers for 10 years. Not once has two showers been on at the same time. |
On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote:
Many thanks to Andy Hall and others for their help earlier this year on the design of my new plumbing system (http://tinyurl.com/3pwck etc.). Unfortunately, thanks to a few months illness, I'm still at it - with a few issues to resolve. A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? My feeling is that it isn't. At worst, I would guess that only one shower and the bath would be running concurrently. Even so, a power shower consumes 15 lpm and a bath consumes 20 lpm. Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... [For information, the hot water will be heated indirectly in a 250 litre tank by a condensing boiler. The mains supply pressure will be reduced (to 2 bar?) by a water softener, although a "high flow" softener, such as the Kinetico 2020c HF, will be fitted to minimise this problem.] Presumably the central heating could operate as a sealed system, even if the hot water tank is vented? Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. Did the Water Company section in the road get replaced all the way to the main? or just to the meter? or just to the property boundary. How was the 25 lpm derived? The are all sorts of tanks for using the eaves and apex of roof spaces if that is an issue. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html |
"Ed Sirett" wrote in message n.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: Many thanks to Andy Hall and others for their help earlier this year on the design of my new plumbing system (http://tinyurl.com/3pwck etc.). Unfortunately, thanks to a few months illness, I'm still at it - with a few issues to resolve. A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? My feeling is that it isn't. At worst, I would guess that only one shower and the bath would be running concurrently. Even so, a power shower consumes 15 lpm and a bath consumes 20 lpm. Is there any way around this problem? A pump and hydraulic accumulator sounds expensive. Due to a loft conversion, there is not any convenient space for a cistern, although I'm thinking that I may have to create some... [For information, the hot water will be heated indirectly in a 250 litre tank by a condensing boiler. The mains supply pressure will be reduced (to 2 bar?) by a water softener, although a "high flow" softener, such as the Kinetico 2020c HF, will be fitted to minimise this problem.] Presumably the central heating could operate as a sealed system, even if the hot water tank is vented? Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. Is the stop cock a full one? |
On Wed, 6 Oct 2004 12:36:40 +0100, "John Aston"
wrote: Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". This rather suggests that their main is limited. The best thing that you can do is to look at all the components after the service pipe. e.g. stop cock full bore lever ball valve, 22mm pipe internally to key points or 28mm for anything of any length, avoid too many bends. Space in my loft is very limited, but I do have basement space so I could get an accumulator. GAH make a "Dualstream" accumulator but you have to buy their rebadged Ariston unvented hot water cylinder with it. I don't know anything about the quality of Ariston. For a 300 litre accumulator and 300 litre cylinder the list price is £2112 (less 40% from a distributor I'm told!). The 300 litre accumulator is 5'2" high and almost 2' diameter so it takes up a lot of room. I suppose that I'll have to compare the Dualstream cost with a "cistern and pump" solution and take a view on it. This is an expensive hobby. I think that IMM's idea of some storage above the HW cylinder is interesting, if you have the height. However, be careful about making the HW cylinder too small because you risk running out of hot water for the bath. However...... I don't subscribe to the notion of a combi with small store running two showers and certainly not a shower and a bath for three reasons: - The amount of stored energy is small and once it runs out, the performance is very poor. - The hot water is mixed with very little cold in the winter, so the run time will be quite short. - You are still governed by the total delivery of water from the main. I think that I would try to look for different ways to store cold water high up before getting into accumulators. If it really doesn't add up, then this may be the sensible option though. ..andy To email, substitute .nospam with .gl |
"Andy Hall" wrote in message ... On Wed, 6 Oct 2004 12:36:40 +0100, "John Aston" wrote: Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". This rather suggests that their main is limited. The best thing that you can do is to look at all the components after the service pipe. e.g. stop cock full bore lever ball valve, 22mm pipe internally to key points or 28mm for anything of any length, avoid too many bends. Space in my loft is very limited, but I do have basement space so I could get an accumulator. GAH make a "Dualstream" accumulator but you have to buy their rebadged Ariston unvented hot water cylinder with it. I don't know anything about the quality of Ariston. For a 300 litre accumulator and 300 litre cylinder the list price is £2112 (less 40% from a distributor I'm told!). The 300 litre accumulator is 5'2" high and almost 2' diameter so it takes up a lot of room. I suppose that I'll have to compare the Dualstream cost with a "cistern and pump" solution and take a view on it. This is an expensive hobby. I think that IMM's idea of some storage above the HW cylinder is interesting, if you have the height. However, be careful about making the HW cylinder too small because you risk running out of hot water for the bath. However...... snip tripe And you were doing so well up until now. 5/10 |
IMM wrote in message ... I assume you haven't bought any equipment yet. That's correct. In your situation which I assume you have 1 bath and two showers, and I would go: 1. Combi boiler (to do the two showers only) 2. A "combination" cylinder with quick recovery coil. (cold tank and hot cylinder all in one space saving unit). This operates at low pressure http://www.rcmgroup.co.uk/specialized.htm RCM will make a large cold tank section for you. They will ake the hot and cold section sizes to order. The CH side of the combi acts as a normal system boiler heating the cylinder and CH. The cylinder does the bath and therest of the house to give good fillups. The water side of the combi only does high pressure showers. Something like an Alpha CB50, W-B Greenstar high flow condensing combi would do. The W-B Greenstar 40kW model can deliver 16 litres/min and you need to add cold to the showers, so a decent shower had if two on at the same time. This approach is cost effective and no power shower pump used. Sorry, I'm misunderstanding something here. I thought that the total flow rate was limited by the available flow rate at the incoming service pipe. Or is hot water stored in the combi boiler and pumped to the shower on demand? Apologies for my ignorance. Will you really have the bath filling and a shower on at the same time? A relative has had a single shower power shower pump serving two showers for 10 years. Not once has two showers been on at the same time. I would like to budget for a bath and shower that are on simultaneously. I have a large family. |
"John Aston" wrote in message .. . IMM wrote in message ... I assume you haven't bought any equipment yet. That's correct. In your situation which I assume you have 1 bath and two showers, and I would go: 1. Combi boiler (to do the two showers only) 2. A "combination" cylinder with quick recovery coil. (cold tank and hot cylinder all in one space saving unit). This operates at low pressure http://www.rcmgroup.co.uk/specialized.htm RCM will make a large cold tank section for you. They will ake the hot and cold section sizes to order. The CH side of the combi acts as a normal system boiler heating the cylinder and CH. The cylinder does the bath and therest of the house to give good fillups. The water side of the combi only does high pressure showers. Something like an Alpha CB50, W-B Greenstar high flow condensing combi would do. The W-B Greenstar 40kW model can deliver 16 litres/min and you need to add cold to the showers, so a decent shower had if two on at the same time. This approach is cost effective and no power shower pump used. Sorry, I'm misunderstanding something here. I thought that the total flow rate was limited by the available flow rate at the incoming service pipe. Or is hot water stored in the combi boiler and pumped to the shower on demand? Apologies for my ignorance. Stored water in the combination cylinder for all the house giving a good flow, which is not on the mains. The combi cylinder is the bottom right. http://www.rcmgroup.co.uk/specialized.htm The mains only supplying the two showers via the combi boiler giving high pressure showers with a power shower pump. The Alpha CB50 is a stored water combi, the Greenstar is not. Will you really have the bath filling and a shower on at the same time? A relative has had a single shower power shower pump serving two showers for 10 years. Not once has two showers been on at the same time. I would like to budget for a bath and shower that are on simultaneously. I have a large family. That is fine. Some people tend to oversize water systems. If one bath and one shower simultaneously then the combination cylinder with a quick recovery coil and a combi boiler doing only the showers is the way. I assume the bath will be below or on the same level as the cylinder? If so, then no problems. |
Ed Sirett wrote in message n.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: snip A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? snip Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. Better than an accumulator? I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. I wonder if the water meter could be resticting the flow significantly. Did the Water Company section in the road get replaced all the way to the main? or just to the meter? or just to the property boundary. The 32mm MDPE pipe was laid by me from the water meter point at the boundary of my property to the main stopcock in my house (a distance of 45m). How was the 25 lpm derived? Unfortunately I wasn't present when the Cambridge Water engineer came to measure the flow rate, so I don't know how the figure of 25 lpm was derived. My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" very substantial, particularly if is to be shared among appliances. The are all sorts of tanks for using the eaves and apex of roof spaces if that is an issue. Thanks. I'll look around. |
"IMM" wrote in message ... "John Aston" wrote in message .. . IMM wrote in message ... I assume you haven't bought any equipment yet. That's correct. In your situation which I assume you have 1 bath and two showers, and I would go: 1. Combi boiler (to do the two showers only) 2. A "combination" cylinder with quick recovery coil. (cold tank and hot cylinder all in one space saving unit). This operates at low pressure http://www.rcmgroup.co.uk/specialized.htm RCM will make a large cold tank section for you. They will ake the hot and cold section sizes to order. The CH side of the combi acts as a normal system boiler heating the cylinder and CH. The cylinder does the bath and therest of the house to give good fillups. The water side of the combi only does high pressure showers. Something like an Alpha CB50, W-B Greenstar high flow condensing combi would do. The W-B Greenstar 40kW model can deliver 16 litres/min and you need to add cold to the showers, so a decent shower had if two on at the same time. This approach is cost effective and no power shower pump used. Sorry, I'm misunderstanding something here. I thought that the total flow rate was limited by the available flow rate at the incoming service pipe. Or is hot water stored in the combi boiler and pumped to the shower on demand? Apologies for my ignorance. Stored water in the combination cylinder for all the house giving a good flow, which is not on the mains. The combi cylinder is the bottom right. http://www.rcmgroup.co.uk/specialized.htm The mains only supplying the two showers via the combi boiler giving high pressure showers with a power shower pump. The Alpha CB50 is a stored water combi, the Greenstar is not. Will you really have the bath filling and a shower on at the same time? A relative has had a single shower power shower pump serving two showers for 10 years. Not once has two showers been on at the same time. I would like to budget for a bath and shower that are on simultaneously. I have a large family. That is fine. Some people tend to oversize water systems. If one bath and one shower simultaneously then the combination cylinder with a quick recovery coil and a combi boiler doing only the showers is the way. I assume the bath will be below or on the same level as the cylinder? If so, then no problems. Combination cylinders: http://www.rcmgroup.co.uk/Direct&Indirect.htm They have units with in litres: hot : cold 115: 160 115: 228 The large cold storage means you can have a the cold section supplying the hot and cold in the house and a 15mm pipe filling the unit. The showers are via the combi. |
"John Aston" wrote in message .. . Ed Sirett wrote in message n.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: snip A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? snip Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. Better than an accumulator? I think Ed means a basement located tank with a pressure pump doing all the house, hot and cold. I prefer the combination cylinder. I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. I wonder if the water meter could be resticting the flow significantly. They sometimes do. Make sure you have a full bore 1/4 turn stop cock. Did the Water Company section in the road get replaced all the way to the main? or just to the meter? or just to the property boundary. The 32mm MDPE pipe was laid by me from the water meter point at the boundary of my property to the main stopcock in my house (a distance of 45m). How was the 25 lpm derived? Unfortunately I wasn't present when the Cambridge Water engineer came to measure the flow rate, so I don't know how the figure of 25 lpm was derived. My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" very substantial, particularly if is to be shared among appliances. The garden hose is usually at the end a run in 15 mm pipe running through double check valve. If you can, take a large bore hose directly from the stop cock and measure that. If it is substantially better then run 22mm to any mains fed appliances. The are all sorts of tanks for using the eaves and apex of roof spaces if that is an issue. Thanks. I'll look around. |
Andy Hall wrote:
On Wed, 6 Oct 2004 12:36:40 +0100, "John Aston" wrote: Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". This rather suggests that their main is limited. You cannot be seriosu. Any main that feeds more than a couple of houses will be large enough to feed one at high volume. I think I am at about 3 bar hgere and water simply gushes out. My main restriction is internal pipework and the water softener. The best thing that you can do is to look at all the components after the service pipe. e.g. stop cock full bore lever ball valve, 22mm pipe internally to key points or 28mm for anything of any length, avoid too many bends. Totally agree here. |
"John Aston" wrote in message .. . My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" very substantial, particularly if is to be shared among appliances. My outdoor tap delivers water at less than half the rate that I can get at another tap internally. I have no idea why this is since I didn;t fit the tap and I really don't need lots of water delivered quickly in the garden. However, you might find that your outdoor tap is similarly slow compared to your internal, and you might be in better shape than you think. Neil |
On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston"
wrote: Many thanks to Andy Hall and others for their help earlier this year on the design of my new plumbing system (http://tinyurl.com/3pwck etc.). Unfortunately, thanks to a few months illness, I'm still at it - with a few issues to resolve. A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? Hi, Before going for an expensive solution it may be worth checking that they don't mean 25lpm _at_ 2.8 bar. Also a garden tap is quite restrictive, a better measure would be to open all direct mains taps at a time when the mains water pressure is likely to be lowest. [For information, the hot water will be heated indirectly in a 250 litre tank by a condensing boiler. The mains supply pressure will be reduced (to 2 bar?) by a water softener, although a "high flow" softener, such as the Kinetico 2020c HF, will be fitted to minimise this problem.] Presumably the central heating could operate as a sealed system, even if the hot water tank is vented? One way round could be to use the hot tank as a heat bank with a tanked supply for the bath and direct mains for the showers, both heated via separate plate exchangers. cheers, Pete. |
"Pete C" wrote in message ... On Wed, 6 Oct 2004 00:40:02 +0100, "John Aston" wrote: Many thanks to Andy Hall and others for their help earlier this year on the design of my new plumbing system (http://tinyurl.com/3pwck etc.). Unfortunately, thanks to a few months illness, I'm still at it - with a few issues to resolve. A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? Hi, Before going for an expensive solution it may be worth checking that they don't mean 25lpm _at_ 2.8 bar. Also a garden tap is quite restrictive, a better measure would be to open all direct mains taps at a time when the mains water pressure is likely to be lowest. [For information, the hot water will be heated indirectly in a 250 litre tank by a condensing boiler. The mains supply pressure will be reduced (to 2 bar?) by a water softener, although a "high flow" softener, such as the Kinetico 2020c HF, will be fitted to minimise this problem.] Presumably the central heating could operate as a sealed system, even if the hot water tank is vented? One way round could be to use the hot tank as a heat bank with a tanked supply for the bath and direct mains for the showers, both heated via separate plate exchangers. The initial problem is that he "thinks" his mains water supply can't handle demand. A "full" mains pressure system appears out of the question. He needs to assess the proper flowrate and pressure of his supply. He may be OK. If the mains is fine then a heat bank would be fine. One plate should be fine with one bath and 2 showers. If the mains is not that good then an element of stored water is required. He could use a cold tank/cylinder setup heated to 70-80C with the draw-off blended down, via a blending valve, to 50-55C. A bronze pump could pump water out of the cylinder into a plate heat exchanger which will provide mains fed showers. I did that for a neighbour, who wanted a power shower. It was about the same price to buy the plate and pump, etc, at the time. In this case, if the mains can't cope, I would most likely go for a: - combination cylinder for all low pressure hot water - high flow combi for mains showers. Divide and rule. A combination cylinder is about the same size as an unvented cylinder but on low pressure, so no BBA approved fitter or large overflows, pressure safety devices, etc. |
"Neil Jones" wrote in message
... "John Aston" wrote in message .. . My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" "feel" very substantial, particularly if is to be shared among appliances. My outdoor tap delivers water at less than half the rate that I can get at another tap internally. I have no idea why this is since I didn;t fit the tap and I really don't need lots of water delivered quickly in the garden. However, you might find that your outdoor tap is similarly slow compared to your internal, and you might be in better shape than you think. Neil Well, the garden tap does have its own stopcock and a double check valve in line, so you could be right. I'll do a test to see how long it takes to fill a large bucket from the main supply stopcock where water comes in to the house... |
"The Natural Philosopher" wrote in message ... snip I think I am at about 3 bar hgere and water simply gushes out. My main restriction is internal pipework and the water softener. Just out of interest, is your water softener a high flow type? Does it feed a vented or unvented hot water system? |
"John Aston" wrote in message ... "Neil Jones" wrote in message ... "John Aston" wrote in message .. . My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" "feel" very substantial, particularly if is to be shared among appliances. My outdoor tap delivers water at less than half the rate that I can get at another tap internally. I have no idea why this is since I didn;t fit the tap and I really don't need lots of water delivered quickly in the garden. However, you might find that your outdoor tap is similarly slow compared to your internal, and you might be in better shape than you think. Neil Well, the garden tap does have its own stopcock and a double check valve in line, so you could be right. I'll do a test to see how long it takes to fill a large bucket from the main supply stopcock where water comes in to the house... Then if it has a conventional stop cock replace it with a 1/4 turn full bore one (get a good quality one). And then see if the flow increase. I have found a 25% improvement in flow in some cases when replacing old stop cocks. In borderline cases, like yours it is essential to fit these. Also any cold feed should be large bore and bends used. |
On Thu, 07 Oct 2004 08:50:55 +0100, The Natural Philosopher
wrote: Andy Hall wrote: On Wed, 6 Oct 2004 12:36:40 +0100, "John Aston" wrote: Hi, Andy. Unfortunately, I have already replaced the service pipe with a new 32mm diameter pipe. Cambridge Water tell me that they can't do anything about the flow/pressure "because the supply is fed directly from a reservoir". This rather suggests that their main is limited. You cannot be seriosu. Any main that feeds more than a couple of houses will be large enough to feed one at high volume. I was really referring to the statement from the supplier. If the flow is being measured at the end of the 32mm service pipe, the pressure was 2.8 bar and the flow only 25lpm, it suggests that something else is wrong. I think I am at about 3 bar hgere and water simply gushes out. My main restriction is internal pipework and the water softener. The best thing that you can do is to look at all the components after the service pipe. e.g. stop cock full bore lever ball valve, 22mm pipe internally to key points or 28mm for anything of any length, avoid too many bends. Totally agree here. ..andy To email, substitute .nospam with .gl |
Neil Jones wrote:
"John Aston" wrote in message .. . My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" very substantial, particularly if is to be shared among appliances. My outdoor tap delivers water at less than half the rate that I can get at another tap internally. I have no idea why this is since I didn;t fit the tap and I really don't need lots of water delivered quickly in the garden. However, you might find that your outdoor tap is similarly slow compared to your internal, and you might be in better shape than you think. Non return valves? They slow it down a lot. Neil |
"The Natural Philosopher" wrote in message ... Neil Jones wrote: "John Aston" wrote in message .. . My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" very substantial, particularly if is to be shared among appliances. My outdoor tap delivers water at less than half the rate that I can get at another tap internally. I have no idea why this is since I didn;t fit the tap and I really don't need lots of water delivered quickly in the garden. However, you might find that your outdoor tap is similarly slow compared to your internal, and you might be in better shape than you think. Non return valves? They slow it down a lot. It is compulsory to have one on an outside tap. |
John Aston wrote:
"The Natural Philosopher" wrote in message ... snip I think I am at about 3 bar hgere and water simply gushes out. My main restriction is internal pipework and the water softener. Just out of interest, is your water softener a high flow type? Does it feed a vented or unvented hot water system? High flow ish. Its on 22mm copper feeds. System is unvented. One shower at a time and its totally fabulous. Skin ripped off back etc. Two showers together is only as good as yer typical large combi. Pipework is mixture of 22mm and 15mm. |
IMM wrote:
"The Natural Philosopher" wrote in message ... Neil Jones wrote: "John Aston" wrote in message t... My own test was very empirical - I switched off all water supplied to the house and turned on the garden hose. The jet of water did not "feel" very substantial, particularly if is to be shared among appliances. My outdoor tap delivers water at less than half the rate that I can get at another tap internally. I have no idea why this is since I didn;t fit the tap and I really don't need lots of water delivered quickly in the garden. However, you might find that your outdoor tap is similarly slow compared to your internal, and you might be in better shape than you think. Non return valves? They slow it down a lot. It is compulsory to have one on an outside tap. True, but utterly irrelevant. |
"John Aston" wrote in message ... I'll do a test to see how long it takes to fill a large bucket from the main supply stopcock where water comes in to the house... I did the test at 8.30 this morning. My main stopcock in the house is a 32mm bore quarter-turn valve*. I couldn't take the water directly from the stopcock outlet. It had to first go through a straight 2m run of 15mm pipe before I could discharge it into a bucket. (*Note: There is also a 25mm quarter-turn stopcock at the water meter end of the supply pipe.) I comfortably filled two 15 litre buckets in one minute. |
"John Aston" wrote in message ... "John Aston" wrote in message ... I'll do a test to see how long it takes to fill a large bucket from the main supply stopcock where water comes in to the house... I did the test at 8.30 this morning. My main stopcock in the house is a 32mm bore quarter-turn valve*. I couldn't take the water directly from the stopcock outlet. It had to first go through a straight 2m run of 15mm pipe before I could discharge it into a bucket. (*Note: There is also a 25mm quarter-turn stopcock at the water meter end of the supply pipe.) I comfortably filled two 15 litre buckets in one minute. Your problems appear over. 30 litres/min is good enough. This should be fine for 2 showers and one bath on a mains pressure system. Go for: 1. A heat bank 2. More cost effective: View two combi boilers. One doing one zone of space heating (upstairs) the other doing another (downstairs). Each boiler will have a programmer/stat for each zone, preferably a Honeywell CM67, or equiv. Combine the DHW outlets just before the bath using non-return valves and a small shock arrestor expansion vessel, as per Worcester-Bosch Tech dept. It will fill a bath pronto and give good power showers for two showers. With combi's the most important figure is the flowrate. 11 litres/min is fine for showes and the odd slow filling bath. Here is a recent post of mine... For an even better flow rate and cheap too for what you get, assess using two Worcester-Bosch Junior combi's. For high flowrates it is cost effective to use two Juniors and combine the DHW outlets. Worcester-Bosch will supply a drawing on how to do it, or ask me here. Two Juniors are available for around £1000 to £1100 depending on what sized units you buy. They have 24 and 28 kW models, you could one 24kW and one 28 kW. That is cheaper than the Worcester HighFlow 18 litres/min floor mounted combi and can deliver about 21.5 litres/min @ 35 degree temp rise and never run out of hot water. The highest flowrates of any infinitely continuous combi is 22 litres/min @ 30 litre/min temp rise, which is the ECO-Hometec which costs near £2K. Have one combi do the downstairs heating on its own programmer/timer (Honeywell CM67 or equiv) and one do upstairs. No complex and space consuming zone valves used. Natural zoning, so you don't have to heat upstairs when you are not up there saving fuel. The running cost will be approx the same as a condensing boiler heating the whole house. No external zone valves either, and simple wiring up too. The Juniors are simple and don't even have internal 3-way valves. If having two showers, have the shower split between the combi's to reduce influence from one to the other. Also if one goes down you will have another combi to give some heat in the house and DHW too. Combine the outlets for the DHW bath pipes and all the baths you want very quickly and no waiting. Best have the showers on separate combi's. Do not exceed the gas meter flowrate of 212 cu foot per hour. To calulate, e.g., a boiler is 100,000 BTU/hr "input". Divide by 1000 giving 100 cu foot per hour. Add up all the appliances. The Juniors are not condensing combi's, yet overall heating costs will be equivalent to one condensing boiler as the upstairs will not be heated most of the time. A win, win, situation. Its advantages a - cheap to install. - quick to install. - space saving (releases an airing cupboard). Both can go in the loft, or at the back of the existing airing cupboard. - never without heat in the house as two boioers are used. - high flowrates (will do two showers and fill a bath in few minutes), - No waiting for a cylinder to re-heat - Natural zoning, one does upstairs and one does down - hardly any electrical control work (running a wire to a programmers/stat and power to each, - simple no brainer installation, - minimal components used. - less piping used - cheap to run overall as upstairs would be off most of the time - etc. |
On Fri, 8 Oct 2004 10:27:16 +0100, "John Aston"
wrote: "John Aston" wrote in message ... I'll do a test to see how long it takes to fill a large bucket from the main supply stopcock where water comes in to the house... I did the test at 8.30 this morning. My main stopcock in the house is a 32mm bore quarter-turn valve*. I couldn't take the water directly from the stopcock outlet. It had to first go through a straight 2m run of 15mm pipe before I could discharge it into a bucket. (*Note: There is also a 25mm quarter-turn stopcock at the water meter end of the supply pipe.) I comfortably filled two 15 litre buckets in one minute. OK. That changes the picture completely. You can go for the planned pressurised storage system and get very good results. Two things. Make sure that you go for a large enough HW cylinder - I would suggest a 150litre one or more. I have a 200 litre HW cylinder for similar requirements to yours and it does the job admirably, even in coldest weather. The other thing is to plan the internal pipe sizes carefully. If the water softener is a long way from the stop tap then perhaps a 28mm pipe to it, but certainly 22mm. For the run from there to the HW cylinder, 22mm. If there is a run for cold water to several bathroom taps make that 22mm as well. You can then drop down to smaller sizes closer to the taps or fit flow restrictors. The trick becomes to size and arrange things to provide reasonable flow balancing. ..andy To email, substitute .nospam with .gl |
John Aston wrote:
I comfortably filled two 15 litre buckets in one minute. Check the flow rate again at 6.30pm on a weekday. IME a 2:1 variation can be experienced. Regards Capitol |
Andy Hall wrote:
On Fri, 8 Oct 2004 10:27:16 +0100, "John Aston" wrote: "John Aston" wrote in message ... I'll do a test to see how long it takes to fill a large bucket from the main supply stopcock where water comes in to the house... I did the test at 8.30 this morning. My main stopcock in the house is a 32mm bore quarter-turn valve*. I couldn't take the water directly from the stopcock outlet. It had to first go through a straight 2m run of 15mm pipe before I could discharge it into a bucket. (*Note: There is also a 25mm quarter-turn stopcock at the water meter end of the supply pipe.) I comfortably filled two 15 litre buckets in one minute. OK. That changes the picture completely. You can go for the planned pressurised storage system and get very good results. Two things. Make sure that you go for a large enough HW cylinder - I would suggest a 150litre one or more. I have a 200 litre HW cylinder for similar requirements to yours and it does the job admirably, even in coldest weather. The other thing is to plan the internal pipe sizes carefully. If the water softener is a long way from the stop tap then perhaps a 28mm pipe to it, but certainly 22mm. For the run from there to the HW cylinder, 22mm. If there is a run for cold water to several bathroom taps make that 22mm as well. You can then drop down to smaller sizes closer to the taps or fit flow restrictors. The trick becomes to size and arrange things to provide reasonable flow balancing. I second this advice in every detail. Essentially its what I have, and it works well. .andy To email, substitute .nospam with .gl |
On Thu, 07 Oct 2004 01:23:30 +0100, John Aston wrote:
Ed Sirett wrote in message n.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: snip A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? snip Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. Better than an accumulator? The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. I wonder if the water meter could be resticting the flow significantly. It does not make a problem elsewhere. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html |
"Ed Sirett" wrote in message .co.uk... On Thu, 07 Oct 2004 01:23:30 +0100, John Aston wrote: Ed Sirett wrote in message n.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: snip A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? snip Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. Better than an accumulator? The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. Best have a phosphor in-line descaler. I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. I wonder if the water meter could be resticting the flow significantly. It does not make a problem elsewhere. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html |
Ed Sirett wrote in message .co.uk... snip The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. snip Is this your personal experience? The Kinetico 2020c High Flow Softener has a service flow rate of 33 lpm and a peak flow rate of 51 lpm. Providing that I use a suitably large pipe diameter, is this really going to appreciably slow down my 30 lpm supply? |
On Sat, 9 Oct 2004 23:40:52 +0100, "John Aston"
wrote: Ed Sirett wrote in message n.co.uk... snip The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. snip Is this your personal experience? The Kinetico 2020c High Flow Softener has a service flow rate of 33 lpm and a peak flow rate of 51 lpm. Providing that I use a suitably large pipe diameter, is this really going to appreciably slow down my 30 lpm supply? There are some things that you can do to mitigate this: - Look for the highest flow model that makes sense. This does not necessarily mean picking one that is suitable for a larger number of people in the house - that is more of an issue with single chamber machines which regenerate at night, and those for more people simply have a larger resin chamber to be able to deliver a greater volume of water over a day. You can get commercial models with higher flow, but they get rapidly expensive.. If you look at specs. you can ask the suppliers for their flow/pressure graphs (for the system, not just the valve) and pick from these. Some machines have 1" rather than 3/4" fittings which can help. - You can get wide bore hoses. Often, the ones normally supplied have as little as 12mm bore, so it's useful to get larger ones. I replaced mine on a Kinetico a while ago and it did help somewhat. - The stop valves supplied with the machines are sometimes not full bore. You can use 22mm or as discussed before, 28mm quarter turn lever ball valves. - You have to have a double check valve with a water softener, and these do tend to restrict flow. You can fit a larger one than that implied by the pipe - e.g. a 28mm one on a 22mm pipe. ..andy To email, substitute .nospam with .gl |
On Sat, 09 Oct 2004 23:40:52 +0100, John Aston wrote:
Ed Sirett wrote in message .co.uk... snip The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. snip Is this your personal experience? The Kinetico 2020c High Flow Softener has a service flow rate of 33 lpm and a peak flow rate of 51 lpm. Providing that I use a suitably large pipe diameter, is this really going to appreciably slow down my 30 lpm supply? Yes this is my diret experience at one site. It would clearly not have been had they used the Kinetico High Flow unit which I expect is a tad more pricy than a typical unit. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html |
On Sat, 09 Oct 2004 23:02:00 +0100, IMM wrote:
"Ed Sirett" wrote in message .co.uk... On Thu, 07 Oct 2004 01:23:30 +0100, John Aston wrote: Ed Sirett wrote in message n.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: snip A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? snip Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. Better than an accumulator? The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. Best have a phosphor in-line descaler. As to whether this is best or not will depend on the reason the OP wishes to threat the water. Adding phosphates is not the same as exchanging ions and that's not the same as removing ions. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html |
"Ed Sirett" wrote in message . co.uk... The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. Best have a phosphor in-line descaler. As to whether this is best or not will depend on the reason the OP wishes to threat the water. Adding phosphates is not the same as exchanging ions and that's not the same as removing ions. This is a borderline mains pressure system. Anything that may restrict flow/pressure should be avoided. Most people only want to descale. A phosphor canister does that well and does not restrict flow. |
Ed Sirett wrote:
On Thu, 07 Oct 2004 01:23:30 +0100, John Aston wrote: Ed Sirett wrote in message mon.co.uk... On Wed, 06 Oct 2004 00:40:02 +0100, John Aston wrote: snip A question regarding an unvented domestic hot water system: Cambridge Water tested my incoming main supply and informed me that the pressure = 2.8 bar and the flow rate = 25 litres per minute. Is this sufficiently high for an unvented supply feeding a family home containing two power showers, a bath, five sinks, three toilets, a washing machine and a dishwasher? snip Given that you want to soften the water I strongly think that a pumped storage cistern approach will be best. Better than an accumulator? The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. No. just *A* bottle neck. Mine is totally capable if one shower at insane flows, and two showers at normal flows. I'm really surprised that 2.8 bar static on 32mm (25mm inside) MDPE pipe gives only 25lpm. This implies that the supply in the road is somewhat restrictive. I wonder if the water meter could be resticting the flow significantly. It does not make a problem elsewhere. |
IMM wrote:
"Ed Sirett" wrote in message . co.uk... The problem is that a water softener is a _huge_ restriction on the flow and with any form of direct HW systems it will be the bottle neck. Best have a phosphor in-line descaler. As to whether this is best or not will depend on the reason the OP wishes to threat the water. Adding phosphates is not the same as exchanging ions and that's not the same as removing ions. This is a borderline mains pressure system. Anything that may restrict flow/pressure should be avoided. Most people only want to descale. That is simply not true. Most people want to eliminate nasty scums from their baths, and scale deposits as well. A phosphor canister does that well and does not restrict flow. |
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