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Central Heating

Hot water getting drained from condensation outlet constantly, please help

Anonymous user 26 March 2021 - 5.38 AM

Hi I have a vaillant ecotec plus 937 boiler and since last few days I can hear that water in constantly getting drained out from condensation outlets and the boiler keeps on getting fired every few min. I can’t see any faults on the display either. I have tried to turn off the comfort mode but still the doesn’t seem to stop draining, any suggestions/advise would be helpful. On further examination it appears that that the water is flowing out from pressure relief valve , which has a blue cap and 10 bar. Additionally the water is flowing out even if I turn off the boiler. With the expansion vessel, I have removed the condensation water changed the schrader valve core and charged the vessel to 1 bar and the pressure seems to retain so far. Not sure if this will change the root cause of water draining down the PRV. Thanks, A

4 answers from MyBuilder tradespeople


26 March 2021



Anonymous user

Expansion vessel has got pin holes in side it and making it over heating and discharge


29 March 2021


Pipeline Plumbing Ltd
Rating: 4.9 out of 54.9538 reviews
Welwyn Garden City

If you’ve charged the expansion vessel and the vessel is holding the charge then probably the pressure relief valve needs to be changed as it’s letting by. Sometimes when these activate initially they never go back to working order


10 April 2021


Blake Home Services
Rating: 5 out of 55511 reviews

Boiler should be checked by a professional. PRV's in boilers are not usually set to 10 bar. It sounds like the filling loop is running all the time, which often happens on Vaillants . So isolate the cold main and see if it still happens.


14 April 2021