Discuss Temperature relief unvented cylinder in the USA area at PlumbersForums.net
Thank you I have just taken them apart it's the 6bar expansion relief valve on the incoming main that's letting by have recharged expansion vessel and is still letting by. Its a direct cylinder.You sure you mean the combined temperature and pressure relief valve? The 7 bar 95°c one?
Is it fed by immersion or boiler?
It's most likely a bit of crap stopping the valve from seating properly. Of course it could be sensing excess temperature and that needs investigatin
Its probably not pressure related because the 6 bar expansion relief valve on incoming main should activate first, unless that's faulty. If that's the case you'd need to investigate why the incoming pressure has risen ie, faulty pressure reducing valve etc.
Thanks the expansion vessel was totally empty when I got here. I have recharged and is still dripping. Do they sometimes not reseal correctly when discharged?Crap can and has caused this but usually flushing through would dislodge debris. Any doubts just isolate supply and take off and have a look. I suspect though that if the vessel is sound and of right size and reducing valve is ok then your problem lies elsewhere
I did yes. I dropped pressure and took expansion vessel off as couldn't reach it in place.Are you a 100% sure the vessel hasn't failed? Have you tried dropping the pressure slightly through nipple to see if water appears or air? The vessel as you know is just a rubber diaphragm filled with air and no water should escape from nipple unless the diaphragm had ruptured. Also when you recharged the vessel did you drop the pressure out of the system first?
Its high around 8 bar.What’s the main incoming pressure could be back pressuring
What’s the main incoming pressure could be back pressuring
Do you mean feedback which is what we've discussed above?
Thanks I think my next step would be to swap the composite valve then.Yes that's what hes suggesting and what I had you test for earlier
Thanks I think my next step would be to swap the composite valve then.
Do you mean feed back through a tap? There's one tap, the kitchen tap that has mains pressure one side and 3.5 bar hot water on the other. It's a dual flow tap though. I think.
It hasn't nothis one got a dcv on the hot side ?
Yes thanks very much for your help.
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It hasn't no
I may put a pressure reducer on the main in coming pipe and set to 3.5bar. So it's balanced everywhere.I would fit one and see
I would fit one and see
I may put a pressure reducer on the main in coming pipe and set to 3.5bar. So it's balanced everywhere.
Shaun I advised to isolate cold main into cylinder, drop some pressure out and then see if the PRV started to drip again after enough time for any back feeding to accumulate and it didn't happen, so installing a double check valve is not needed to test correct?
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I would advise one under the kitchen sink on incoming main so as you say it's all balanced, although this is not the current problem
I've never had any issues with them sealing after opening - it's clean water, in theory no rubbish should get under them and thus seal OK.
I've only ever had three fail (where the Expansion has been OK) has been on temperature. One dripped on temperature rise and the other two would open full bore on a temp above 45oc. The other issue is backflow but that seems to have already been discussed.
Daft question - but are you sure it's the Temp/Pressure Relief valve dripping. Many installers tee that in with the blow off from the combination valve before the tundish - could it be this dripping instead? I find more regularly these fail.
Ah yes, I read the first post and skim read the rest!It's the 6 bar expansion relief valve that's the culprit, not the combined pressure and temperature valve mate
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