Losing water through pressure relief valve


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Old 10-15-06, 09:20 AM
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Question Losing water through pressure relief valve

I have a sealed system with a gas boiler. I often find water has come out of the pressure relief valve and the system pressure dropped to less than 1.0 bar. (Happens so often I have a bowl under the bolier to catch it.) I haven't been by boiler when it leaks so don't know if its very gradual or a sudden occurrence. It isn't leaking when boiler is cold.

I top system pressure back up to 1.4 bar, via a mains loop. Having to do this at least once a week. I've read it's not good to be introducing fresh water so often because of potential corrosion.

I checked the expansion vessel, in case diaphragm had gone. No water comes out when I press the pin on the valve. Tyre pressure gauge says it's 0.9 bar. So I think expansion vessel is OK.

Is it likely to be a faulty pressure relief valve? Or could the pressure be getting excessive for another reason and the relief valve is just doing its job?

Any advice much appreciated.
 
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Old 10-15-06, 09:27 AM
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You should check the expansion vessel when the system is empty otherwise you will get incorrect readings.

With the system pressure at 0 bar the exp/vessel pressure should be about 1.0 bar.
 
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Old 10-15-06, 09:57 AM
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Many thanks for the quick reply. You guessed right - I hadn't drained the boiler when I tested the expansion vessel pressure. I'll redo the test.
 
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Old 10-15-06, 02:16 PM
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Expansion Vessel Pressure

You don't have to completely drain the boiler or system, just drop the pressure to zero. This can be done thru the boiler drain or pressure relief valve.
 
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Old 10-15-06, 04:11 PM
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Smile

Thanks Grady for clarifying that I only need to drop pressure to zero and not go mad draining too much. I'll do it through relief valve. Aiming to try this after work tomorrow.
 
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Old 10-22-06, 10:57 AM
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Smile Fixed - Thank you

andyb and Grady
A big thank you for your advice. I've waited quite a time before replying as I didn't think the problem with water coming out of the relief valve was fixed at first. I dropped the pressure to zero and the tyre gauge said I had about 0.2 bar in the expansion vessel. Using a car tyre pump brought it up to 0.8 bar. After the first night's heating I checked the bowl and there was half a cup of water in it. Damn I thought, it ain't fixed. However I've checked every day since and the bowl's been dry. Looks like it's sorted after all. Not just that, the boiler has stopped cycling on and off every few minutes and the radiators are hotter. Never would have guessed the expansion vessel pressure was so important. Great result. Thanks guys.
 
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Old 10-22-06, 11:13 AM
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Wink

Id keep a eye on the tank . You dont know yet if the schrader valve leaked air or sure the diaphragm in the tank is good.

ED
 
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Old 10-22-06, 12:58 PM
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Appreciate you coming back and letting us know how you have got on .

Andy B.
 
 

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