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Plumbing

Central heating flummoxing 3x local plumbers- any help appreciated!

Anonymous user 28/02/2024 - 3.42 PM

I know loads and loads of people have problems with their boiler pressure dropping- probably due to unfound leaks in their central heating system but we have one no local plumber seems to be able to sort so I'm looking for help. In brief, combi boiler and sealed pressurised system. Moved into the house 6y ago and pressure was always dropping- got new expansion vessel, stuck in some leak sealant with no dramatic results. Then did a renovation, so some new plumbing on all three floors and a completely new Worcester Bosch boiler. Pressure drop no better and has gradually got worse year on year. It is an Edwardian terrace house with a tiny sub floor space so looking for leaks has always been a nightmare, but we and 3x plumbing companies have looked under the floor and never seen any leaks but admit they would be a nightmare to spot. No damp patches on the ceilings, though did eventually find one leak under the floor noted due to rising damp which is now (hopefully) fixed. Still pressure dropping. In order to try and narrow down where the leak could be, we have had various valves fitted so we can try and isolate different parts of the house to see where would be worth re-plumbing but no matter which floor we block off (ground, middle or loft) the pressure STILL drops. We figured it must be the boiler but multiple plumbers have checked it and say condensate, PRV, expansion vessel etc all fine. So in the end we gave up and just had the ground floor re-plumbed at no small cost. And the problem is worse rather than better! We top the boiler up from 0 to 1.5bar every day now, the problem is definitely worse the more demand there is on the boiler but I just don't know what to do. I have already spend most of our savings on this and if I could ignore it I would be I now worry we are ruining our new boiler- we have already had to have the heat exchange plates replaced as they clogged up with corrosion from the system and it's less than 3y old. (We now have one of those magnate things) Any advice appreciated, pretty desparate now! I guess my main questions are - could this be the boiler? I just can't understand how despite isolating each floor it keeps dropping - what would you do next? Leak sealant? Leak finding company?

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5 Answers

Anonymous user

I’m not a heating engineer so not giving professional advice, however if it were me I think I would drain system and isolate boiler from the pipe work. Maybe then carry out a pressure test with air to establish if the pressure holds. This may be a way to locate a leak if there is one as you may hear it where you can’t see it ? I could be completely wrong but it’s what I would try as you seem to be at a stop
Answered14 February 2019
1

Anonymous user

If system has been isolated from boiler and pressure still drops at boiler then I would be inclined to say possible leaking main heat exchanger internally that as it warms expands allowing the crack/hole to get bigger therefore causing a larger loss of pressure.
Answered14 February 2019
1

IRVING Plumbing Heating Gas

Rating: 5 out of 5
Margate
Hi nightmare situation. The boiler that has been fitted has been calculated correctly for the size of expansion cessel it holds? I know from the aounds of things you have checked the prv pipe outside (the small copper pipe exiting wall )but. Temporarily place a sandwich bag if poss around its exit. Top up the boiler and run it. Once you realise system has dropped again and need to represurise . Before doing so check bag. If full of water then expansion at fault. only leave on temporarily. If nothing there then looking like leak. Do try prv tho as some once breeched do shut down compleatly looking as though it bever let by. Bit heath robinson but may give you an answer. Discalaimer :No responsibility can be taken by ourselves for any injury or damage caused by you following our free advice. Good luck.
Answered14 February 2019
1

D & R Property and Plumbing Maintenance

Rating: 4.9 out of 5
New Romney
like mr irving says it may well be that the volume of water in your system exceeds the expansion capacity of the boilers expansion vessel,how many rads do you have on system ?,phone worcester bosch tell them size of system they will tell you if you need extra expansion capacity.
Answered14 February 2019
1

Anonymous user

I agree with the above it’s more than likely you require an extra expansion vessel fitting in the return pipe of the central heating. Get a gas Engineer to this for you.
Answered17 February 2019
0