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Combi boiler losing water from drain (Worcester)
No, I haven't gone and bought a combi :-)
A friend has a Worcester 240 combi boiler, about 9 years old. The pressure started dropping a week ago, and it now needs topping up several times a day. Further investigation reveals that it is losing water from the drain that goes to the outside of the house. This isn't a condensing boiler. I have zero experience with combis. Any pointer to what this might be, where to start, etc.? What is this drain? Why is it there? What does it connect to? What could be causing the water loss? TIA -- Grunff |
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"Grunff" wrote in message
... No, I haven't gone and bought a combi :-) A friend has a Worcester 240 combi boiler, about 9 years old. The pressure started dropping a week ago, and it now needs topping up several times a day. Further investigation reveals that it is losing water from the drain that goes to the outside of the house. This isn't a condensing boiler. I have zero experience with combis. Any pointer to what this might be, where to start, etc.? What is this drain? Why is it there? What does it connect to? What could be causing the water loss? TIA -- Grunff Must be the pressure relief valve surely? Perhaps it's got a bit of grit stuck in it? Alex |
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Check that the orange expansion vessel is working correctly. Undo Schraeder valve (bike pump nipple) and move needle asside briefly, is air let out or water? Water? get a new expansion vessel. Air? Check pressure with car pressure guage. To do this, let all pressure out of heating system darin down until pressure guage on boiler reads 0, stop there. What is pressure at Schraeder valve? 0.5 to 1 bar? OK Less? Pump it up with a bike pump. Refill, get heating water jolly hot, turn off and blow it all out of the prv. The hot water jetting out may just clean the seat, but probably won't. If it doesn't work, buy a new prv. To fit, drain boiler (through prv) after isolating flow and return pipes, fit new prv, re-open valves and top up. Job's a goodun. Great combi by the way, wish Worcester were still that good. |
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"Alex (YMG)" wrote in message ... "Grunff" wrote in message ... No, I haven't gone and bought a combi :-) A friend has a Worcester 240 combi boiler, about 9 years old. The pressure started dropping a week ago, and it now needs topping up several times a day. Further investigation reveals that it is losing water from the drain that goes to the outside of the house. This isn't a condensing boiler. I have zero experience with combis. Any pointer to what this might be, where to start, etc.? What is this drain? Why is it there? What does it connect to? What could be causing the water loss? The pressure relief valve will blow off at 2.5 - 3 bar. The pressure of a normal system is somewhere in the 1.5 bar region. To prevent a large pressure increase in the system when the combi fires up the CH, there is a bladder-like air-sac in a big metal doughnut thingy. This is an expansion reservoir that takes up the expansion of water in the system as it heats up, thereby stopping the system pressure climbing to dangerous levels. Your friend's air reservoir ( I forget the proper name for the item ) either has lost all its air via the top-up bicycle valve which is attached to the doughnut, or has a punctured diaphragm inside and has lost all its air into the CH system. Thus, when the CH fires up, the CH water expands, the system pressure rises too far and the last-ditch safety feature, the blow-off valve, does its stuff. You would probably do best to locate the expansion reservoir doughnut ( possibly painted red, at the back of the combi, about a foot across??? ), and see if you can pump it up via the bicycle repressurising valve. Then keep an eye on the system pressure, maybe for several weeks. If the system loses the ability to regulate pressure again, then it'll probably need a new expansion reservoir, 'cause the daphragm will be leaking. Andy. |
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andrewpreece wrote:
You would probably do best to locate the expansion reservoir doughnut ( possibly painted red, at the back of the combi, about a foot across??? ), and see if you can pump it up via the bicycle repressurising valve. Then keep an eye on the system pressure, maybe for several weeks. If the system loses the ability to regulate pressure again, then it'll probably need a new expansion reservoir, 'cause the daphragm will be leaking. And if the diaphragm is totally buggered, when you push the pin on the Schrader valve water will **** out, right? And this means there is no expansion space, so the pressure relief valve blows every time the boiler fires. Got it. We need a new expansion reservoir. Many thanks for the detailed explanation. -- Grunff |
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Grunff wrote:
And if the diaphragm is totally buggered, when you push the pin on the Schrader valve water will **** out, right? And this means there is no expansion space, so the pressure relief valve blows every time the boiler fires. Got it. We need a new expansion reservoir. Many thanks for the detailed explanation. If it is the diaphram, you may find it simpler to just add another expansion chamber elsewhere, rather than trying to get at the original one. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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John Rumm wrote:
Grunff wrote: And if the diaphragm is totally buggered, when you push the pin on the Schrader valve water will **** out, right? And this means there is no expansion space, so the pressure relief valve blows every time the boiler fires. Got it. We need a new expansion reservoir. Many thanks for the detailed explanation. If it is the diaphram, you may find it simpler to just add another expansion chamber elsewhere, rather than trying to get at the original one. Could you explain that a little further? How would one do that? Cheers - Greg |
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"Grunff" wrote
| No, I haven't gone and bought a combi :-) | A friend has a Worcester 240 combi boiler, about 9 years old. | The pressure started dropping a week ago, and it now needs | topping up several times a day. Further investigation reveals | that it is losing water from the drain that goes to the outside | of the house. This isn't a condensing boiler. The 'drain' should be copper pipe, turned back against the wall. It is the outlet of the pressure relief valve and squirts out boiling water. | I have zero experience with combis. Any pointer to what this | might be, where to start, etc.? What is this drain? Why is it | there? What does it connect to? What could be causing the water loss? The pressure valve is opening and releasing water. If the system is within pressure (check gauge on boiler) the valve is faulty. If the system is over pressure then the pressure vessel (which may be within the boiler or elsewhere) is failing. Owain |
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