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Boiler loses pressure but never goes below 0.1 bar - ?

Vaillant Ecotech installed Dec 2010 has always lost pressure but only once lost enough pressure to trigger an error. No matter how well we bleed radiators and refill the boiler, it always drops back down to 0.1 bar. Heating continues no problem at this pressure. We've had a plumber out twice to investigate with no progress so far. No drips from pressure release pipe (had a plastic bag over it for a week). No leaks from radiators and no obvious leaks in ceilings/floors. Logic dictates there's a leak somewhere, but where? And why not lose pressure completely? Any insights would be very helpful. Thanks in advance.

2 Answers from MyBuilder Plumbers

Best Answer

How long does it take the boiler to drain and does it only drain with certain taps used. Ive seen it before where a radiator pipe was mistakenly connected to a bathroom tap so when water was turned on it drained the system. If the boiler never drops below 0.1 either this is a error or the offending pipe is above the boiler so some water remains in the system giving a tiny bit of pressure from gravity.


Answered 27th Jan 2013


You will never loose pressure completely as there is always a supply of water under pressure to your system. I take it you have re-charged the boiler? No obvious leaks could be a problem...depending on how long this has been happening for? If a few days then the leak may show in time...not good as its has had time to damage structure. If no leaks at all and there is no discharge from any warning pipes etc then I would call your boiler supplyer as it should still be under warranty and have them take a look. (Internal problems can and will happen)

Hope this helps.

Titanium Trades


Answered 27th Jan 2013

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