Pressure dropping to 0 on new combi boiler

Ash5ley

I have just changed over from a conventional heating system to a new worcester combi boiler system one week ago.

We are seeing a pressure drop in the system from 1.5 bar to 0 within 4-5 hours. We top up the pressure to 1.5 bar atleast twice a day. Our installer said it must be a CH leak but cannot see any obvious leaks.

Could this pressure drop be only due to a leak within the system or could it be an issue with the boiler.

Thank you for any advice.

JohnB47

There will be an outlet somewhere, to take water from a pressure relief valve. This normally only 'blows' when the pressure reaches an unusually high value, ie over 3 bar. It's unlikely that yourinew system has done that but check for such an outlet and check that it's not showing signs of water. My outlet is a copper pipe on the outside wall near the back of the boiler.

Another way to check is to watch the pressure gauge on the boiler, after you've topped it up and after you fire it up. The guage should go to about 2 or 2.5 bar max.

Otherwise, I'd say that there is a leak in the system somewhere and your installer needs to find the 'non obvious' cause of this. It's his responsibility to diagnose and cure the problem.

I_have_spoken

If old piping has been de-scaled/power-flushed when the combi was installed, it could very easily have opened up pin-holes in the copper which leak at mains pressure. That's one of the risks you take in replacing a open-flue boiler

daveyjp

Go round every radiator and check the vavles were tightened properly after the work. Ours lost pressure due to a loose nut on a towel rail. Less than a quarter of a turn, but it was enough for pressure to escape.

Ash5ley

Thanks everyone for the replies.

@ daveyjp, in your case did you see a visible water leak from the towel radiator which you tightened? We have looked for water/ moisture near all radiator valves and couldnt find anything. Also how quickly did the pressure drop in your case?

Thanks again

macman

As stated in post 2, it could equally be venting from the PRV overflow pipe, go outside and check. Or the EV may be faulty and need repressurising. There is no basis for your installer to assume it's a leak on the CH circuit until he has checked the first two out, which would take just a few minutes.

brewerdave

My daughter had the same problem with a virtually new combi in a new build -finally after many visits by the site plumber and the manufacturer's engineer they did a full strip down & found a pinhole in one of the boiler internal heat exchangers which was discharging the water to the main drain -out of sight out of mind!! We were later told by the plumber that several of the new units had turned up the same fault! Can't remember the make of boiler unfortunately.

Ash5ley

The plumber came today and turned off a couple of vales to check if pressure will drop.

There is no water in the pressure relief valve outside.

j.blimey

sounds like your installer has turned off the flow and return isolation valves under the boiler.Not really recommended, but only for a temporary test.
Hopefully this will rule out the boiler if no significant pressure drop.
Your installer has seen your heating system pipework,radiators,age of,condition of etc and he should have an idea of what to expect unless he is a numpty.
If the existing system looked suspect in relation to age,workmanship etc your installer should have pressure tested the existing circuit before connecting to the boiler.This would prevent water leaking in your property.


Good luck. JB.

arbrighton

We're having a similar issue, although not as quickly- it's over a week or so.

Plumbers didn't find any water on valves (but they wouldn't as it is seeping and hot so would evaporate)

They're going to drain system down and put in something that reacts with air to seal so would seal any pinholes.

The plumbers were not impressive on installation but they must be given a chance for rectification.

Ash5ley

As the pressure was dropping so fast he said that it wont work if we put a sealer into the system.

@ j.blimey - Is it not good for the boiler to do so? The hot water is working in the meantime. The pressure has dropped ever so slightly atm but will wait to see if more significant drop. IF it does drop does it mean its a faulty boiler?