Temperature relief unvented cylinder

[Matt0029]

What can be causing a temperature relief to drip. I have recharged the expansion vessle that had totally lost its charge. I am g3 registered. Thanks

 

[SJB060685]

Thanks I think my next step would be to swap the composite valve then.

The pressure relief valve and or combination valve pressure reducing is my suspicion. I've tried covering everything with you in the hope it only requires one return visit for you

 

[ShaunCorbs]

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.

this one got a dcv on the hot side ?

 

[Matt0029]

Yes thanks very much for your help.
[automerge]1583330917[/automerge]

this one got a dcv on the hot side ?

It hasn't no

 

[ShaunCorbs]

Yes thanks very much for your help.
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It hasn't no

I would fit one and see

 

[Matt0029]

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.

 

[SJB060685]

I would fit one and see

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?
[automerge]1583332686[/automerge]

I may put a pressure reducer on the main in coming pipe and set to 3.5bar. So it's balanced everywhere.

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

 

[ShaunCorbs]

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?
[automerge]1583332686[/automerge]


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

might of caused the original problem tho me and you know they don’t seal good after they’ve discharged

I would say prv on incoming one size larger eg 28mm for a 22mm supply etc

and change the incoming block

 

[EvilDrPorkChop]

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.

 

[SJB060685]

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.

It's the 6 bar expansion relief valve that's the culprit, not the combined pressure and temperature valve mate

 

[EvilDrPorkChop]

It's the 6 bar expansion relief valve that's the culprit, not the combined pressure and temperature valve mate

Ah yes, I read the first post and skim read the rest!

I'd put it down to a faulty 6 bar blow off then, easy enough to replace without replacing the whole combination valve. Had plenty of them fail for no apparent reason, probably most likely from the expansion not working correctly previously.

 

[moonlight]

I you sure its not the cold letting by? pressure reducing valve