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Default Will a Pressure Reducing Valve also Reduce Flow Rate?

Hi. This is a bit complicated so please bear with me.



My incoming water pressure is quite high (about 7 bar - just measured it).
The info' on the new tap I have says it will handle 5 bar max. - above that,
the guarantee isn't valid.



I can currently get about 20 litres/minute flow rate, which, I have read, is
the minimum to run a Combi boiler. I want to install one sometime in the
future.



If I fit a pressure reducing valve (PRV) on the cold supply now, I can use
the tap and also protect the (push-fit) plumbing system from the somewhat
high pressure. But - and this is the actual question - will the PRV have
the unwanted affect of reducing the flow rate, which could prevent a future
Combi from working properly?



And, related to this, are there any PRVs which limit the pressure but not
the flow rate too much.



Thanks



Steve


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Default Will a Pressure Reducing Valve also Reduce Flow Rate?

Steve coughed up some electrons that declared:

Hi. This is a bit complicated so please bear with me.



My incoming water pressure is quite high (about 7 bar - just measured it).
The info' on the new tap I have says it will handle 5 bar max. - above
that, the guarantee isn't valid.



I can currently get about 20 litres/minute flow rate, which, I have read,
is
the minimum to run a Combi boiler. I want to install one sometime in the
future.



If I fit a pressure reducing valve (PRV) on the cold supply now, I can use
the tap and also protect the (push-fit) plumbing system from the somewhat
high pressure. But - and this is the actual question - will the PRV have
the unwanted affect of reducing the flow rate, which could prevent a
future Combi from working properly?



And, related to this, are there any PRVs which limit the pressure but not
the flow rate too much.



Thanks



Steve



You missed my post this very day.

I just went into this in some detail ("MDPE copper unions?" thread).

Firstly: My water pressure is 7.5 bar and no, pushfit doesn't explode - I've
had a bit of JG in service for months and it's been OK.

However, 7+ bar is a bit violent on the tap user and seems to destroy garden
hoses. And your taps do state 5 bar max...

I just ran a bit of 25mm MDPE into the house, jointed to the 1/2 inch
polythene outside. Then a full bore 22mm lever valve, then an Altecnic PRV,
22mm (see the MDPE thread for details, or the G1/4 thread)

Meaurements previously indicated 30-40l/min flow rate.

Now I've thrown 2m of 1/2" pipe away, as well as a manky silly stop cock, I
can now get 50l/min out of the 22mm pipe after the PRV, at any pressure
setting between 2-6 bar. I still have about 15m of 1/2 inch clean bore PE
pipe between me and the road.

That should answer your question. See the mentioned thread for a link to the
PRV I used - you want this one... See also the "Sealing G1/4 pressure gauge
into water pressure regulator" thread for some side fun.

As to your flow - you should get more than 20l/min at 7 bar unless your
incoming pipe is crudded to buggery or your valves or road stopcock are
constricting the flow.

Can you do as I did and swap the incoming parts to full bore valves and
bigger pipe?

See here for mine:

http://photos.dionic.net/v/public/bu..._0019.jpg.html
http://photos.dionic.net/v/public/bu..._0016.jpg.html
http://photos.dionic.net/v/public/bu..._0017.jpg.html

HTH

Tim
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Default Will a Pressure Reducing Valve also Reduce Flow Rate?


"Tim S" wrote in message
...
Steve coughed up some electrons that declared:

Hi. This is a bit complicated so please bear with me.

My incoming water pressure is quite high (about 7 bar - just measured
it).

..
cut.
..
But - and this is the actual question - will the PRV have
the unwanted affect of reducing the flow rate, which could prevent a
future Combi from working properly?

And, related to this, are there any PRVs which limit the pressure but not
the flow rate too much.

Thanks

Steve



You missed my post this very day.

I just went into this in some detail ("MDPE copper unions?" thread).

Firstly: My water pressure is 7.5 bar and no, pushfit doesn't explode -
I've
had a bit of JG in service for months and it's been OK.

However, 7+ bar is a bit violent on the tap user and seems to destroy
garden
hoses. And your taps do state 5 bar max...

I just ran a bit of 25mm MDPE into the house, jointed to the 1/2 inch
polythene outside. Then a full bore 22mm lever valve, then an Altecnic
PRV,
22mm (see the MDPE thread for details, or the G1/4 thread)

Meaurements previously indicated 30-40l/min flow rate.

Now I've thrown 2m of 1/2" pipe away, as well as a manky silly stop cock,
I
can now get 50l/min out of the 22mm pipe after the PRV, at any pressure
setting between 2-6 bar. I still have about 15m of 1/2 inch clean bore PE
pipe between me and the road.

That should answer your question. See the mentioned thread for a link to
the
PRV I used - you want this one... See also the "Sealing G1/4 pressure
gauge
into water pressure regulator" thread for some side fun.

As to your flow - you should get more than 20l/min at 7 bar unless your
incoming pipe is crudded to buggery or your valves or road stopcock are
constricting the flow.

Can you do as I did and swap the incoming parts to full bore valves and
bigger pipe?

See here for mine:

http://photos.dionic.net/v/public/bu..._0019.jpg.html
http://photos.dionic.net/v/public/bu..._0016.jpg.html
http://photos.dionic.net/v/public/bu..._0017.jpg.html

HTH

Tim



Thanks Tim. That's very useful. However I'm not in a position to easily
change the external supply pipe work. The (40-50 year?) old pipe is buried
under the garage floor, then crazy paving, then concrete. It enters the
house in the bathroom, where a small diameter copper pipe supplies an old,
small stopcock.



However changing to a full-bore valve, even a 15mm one, might boost the flow
rate. I'll definitely consider this. Unfortunately the stopcock is located
just above floorboard level in a small space next to the WC; the WC and some
tongue and groove floorboards would have to come out to give working access.
Life's never simple!



A couple of questions about the PRV:

- does it make any/much noise?

- do you know offhand if it's the type that maintains the low pressure all
the time or just when the flow is on (I understand both types exist) ?



Cheers



Steve






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Default Will a Pressure Reducing Valve also Reduce Flow Rate?

Hi Steve,

Steve coughed up some electrons that declared:

Tim


Thanks Tim. That's very useful. However I'm not in a position to easily
change the external supply pipe work. The (40-50 year?) old pipe is
buried
under the garage floor, then crazy paving, then concrete.


It's only worth doing what's practical of course.

It enters the
house in the bathroom, where a small diameter copper pipe supplies an old,
small stopcock.



However changing to a full-bore valve, even a 15mm one, might boost the
flow


There's good odds that could make a noticeable difference. Even if you could
kick it up to 25-30l/min, that will be a big improvement over 20.

I like 1/4 turn valves - quick flick and they're operated rather than
endless turning

rate. I'll definitely consider this. Unfortunately the stopcock is
located just above floorboard level in a small space next to the WC; the
WC and some tongue and groove floorboards would have to come out to give
working access. Life's never simple!


No. I had to tunnel under my foundations to do mine - but that was a "must
do" job as the old pipe ran up the outside of the house!


A couple of questions about the PRV:

- does it make any/much noise?


None that I really notice. I can tell if the taps on round the back, but I'm
not sure if that's pipe wooshing noise or comining from the valve.

It's certainly makes no more noise than one might hear from a bit of exposed
pipe under load.

- do you know offhand if it's the type that maintains the low pressure all
the time or just when the flow is on (I understand both types exist) ?


Mine seems to hold the pressure down. Obviously if I adjust it down with the
taps off, it holds the higher pressure until you let some water out, but it
doesn't appear to creep much over the limit. Static/standing regulation
sometimes runs a bit higher than dynamic regulation (same with gas
regulators) but it seems fairly close.

I'll have a good look today and let you know later exactly how much it
creeps.

Cheers

Tim
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Default Will a Pressure Reducing Valve also Reduce Flow Rate?

Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...

See here for mine:

http://photos.dionic.net/v/public/bu..._0019.jpg.html
http://photos.dionic.net/v/public/bu..._0016.jpg.html
http://photos.dionic.net/v/public/bu..._0017.jpg.html


Good thing to install brass clips either side of the full-bore valve as it
needs to be secure when turning off and on.


My thinking exactly...

I suppose I could have used munsen clips (I have some[1]) screwed onto 10mm
chemical ******s set into the brick.

[1] Munsens are an excellent way of hanging your pipe say 50-70mm off a
rafter so you can get insulation underneath, as I might indeed do...

Operate valve twice a year
off and on to make sure it does not solidify, being 1/4 turn it take 0.5
seconds.


Alwys a good idea with any valve that's vaguely important.

If having a combi or mains pressure water system then always have a 22m
full-bore stoptap and a "dedicated" 22m pipe to the combi or cylinder.
This ensures the cokbi ger priority if say another cold water tap is
turned on.


Or a better idea - throw the combi in the bin. Horrible things!

Cheers

Tim


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Default Will a Pressure Reducing Valve also Reduce Flow Rate?

"Tim S" wrote in message
...

Or a better idea - throw the combi in the bin. Horrible things!


You know nothing of combi boilers to come out with such a dumb comment.
Look at a ~50kW ATAG, 54kW Ethos - quality with flowrates. You can stay in
a body-jet shower with these all day and not run out of DHW. They are
highly cost effective as you would need expensive 500 litre (minimum)
cylinders to do what these can do. The ATAG will deliver 720 litres in 30
minutes and zero time recovery, as it delivers DHW for ever, while the 500
litre cylinder will take over an hour.

W-B 550 (floor mounted).

Any Atmos combi. Vaillant are not bad. Both of these do not have high
flowrate models like ATAG.

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Default Will a Pressure Reducing Valve also Reduce Flow Rate?

Steve coughed up some electrons that declared:


- do you know offhand if it's the type that maintains the low pressure all
the time or just when the flow is on (I understand both types exist) ?


Ok just checked.

Set to exactly 5 bar with tap running slowly.

Turn tap off and it crept up to 5.25bar. So quite a low overshoot.


HTH

Tim
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Doctor Drivel coughed up some electrons that declared:

You can stay in
a body-jet shower with these all day and not run out of DHW.


I don't want to think why *you* would be in the shower all day...

Do they do "Combis Monthly" in a new waterproof and shaggable format now?
With a piccy of the model with the oversized ports and the nice tight jets
on the cover?


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"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:

You can stay in
a body-jet shower with these all day
and not run out of DHW.


I don't want to think why *you* would be in the shower all day...


Do not think.

Do they do "Combis Monthly" in a new waterproof and shaggable format now?
With a piccy of the model with the oversized ports and the nice tight jets
on the cover?


Fantastic idea!

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"Tim S" wrote in message
...
Steve coughed up some electrons that declared:


- do you know offhand if it's the type that maintains the low pressure
all
the time or just when the flow is on (I understand both types exist) ?


Ok just checked.

Set to exactly 5 bar with tap running slowly.

Turn tap off and it crept up to 5.25bar. So quite a low overshoot.


HTH

Tim


Excellent. Many thanks for taking the time/trouble. Steve.




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"Doctor Drivel" wrote in message
...

If having a combi or mains pressure water system then always have a 22m
full-bore stoptap and a "dedicated" 22m pipe to the combi or cylinder.
This ensures the cokbi ger priority if say another cold water tap is
turned on.

Good idea. I'll definitely try for that. 22mm to combi and 15mm to other
stuff. Steve.


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"Steve" wrote in message
...

"Doctor Drivel" wrote in message
...

If having a combi or mains pressure water system then always have a 22mm
full-bore stoptap and a "dedicated" 22mm pipe to the combi or cylinder.
This ensures the combi gets priority if say another cold water tap is
turned on.

Good idea. I'll definitely try for that. 22mm to combi and 15mm to other
stuff. Steve.


Where the coldwater line is teed off, near the stoptap, have an in-line
restrictor. Then you can throttle down the cold. Have the cold line to the
showers off the 22mm line to the combi, just before the combi. Then if a
pressure drop around the combi there will be equal pressure to the showers
hot & cold.

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"Doctor Drivel" wrote in message
...

"Steve" wrote in message
...

"Doctor Drivel" wrote in message
...

..
..
..
Have the cold line to the
showers off the 22mm line to the combi, just before the combi. Then if a
pressure drop around the combi there will be equal pressure to the showers
hot & cold.

Interesting idea. However there will be some extra resistance to flow for
the water passing through the combi's heat exchanger.. Also, in my case,
there will be a much longer path for the water going through the combi
compared to the shower's cold supply.. If the combi and shower cold
supplies are both 22m, then the cold would end up at a higher pressure than
the hot. The answer is a thermostatic shower!


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"Steve" wrote in message
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Have the cold line to the
showers off the 22mm line to the combi, just before the combi. Then if a
pressure drop around the combi there will be equal pressure to the
showers hot & cold.

Interesting idea. However there will be some extra resistance to flow for
the water passing through the combi's heat exchanger.. Also, in my case,
there will be a much longer path for the water going through the combi
compared to the shower's cold supply.. If the combi and shower cold
supplies are both 22m, then the cold would end up at a higher pressure
than the hot. The answer is a thermostatic shower!


Get the situation. 22mm from stoptap to combi. Tee at stoptap and all cold
off this in 15mm. A restrictor on this line, or flow regulator. So you
don't want the shower's cold off this cold line, as if a dishwasher kicks in
the shower's cold will be robbed and DHW will get too hot, cause a temporary
hot blip at the shower which may scald.

The DHW will have a higher resistance than the cold as it runs through the
combi. However, some have less resistance than others, and such great issue.
Do not have 22mm cold to the shower, only 15mm. When there is a pressure
fluctuation around the combi both the DHW and shower cold will be affected
and rise up and down pretty well at teh same rate. The mixer must be "combi
compatible", with a metal thermostatic strip, not a wax operated cartridge.
Best if it has an integral pressure balancing valve, as a combi gives a
reasonable stable temperature output.

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"Steve" wrote in message
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Interesting idea.


Not an idea, it works, it has been done.

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