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Central Heating

Drop in boiler pressure

Anonymous user 03/03/2024 - 3.27 PM

Hi We had a boiler fitted around 8 months ago with underfloor heating for downstairs (so radiators upstairs and UFH downstairs with a manifold). We have renovated the whole house, no carpets in yet. We noticed the boiler pressure drop to 0 after a couple of days. No signs of a leak. We turned the boiler off by the dial on the boiler and the pressure held. Our engineer confirmed there was no leak by doing this. But when we turn the boiler on by the dial and put the heating on, there is still small drops in pressure. Our engineer bled all the radiators and system. Still small drops in pressure. His next step is to place leak seal in the system but I am not comfortable with this. Any ideas why the boiler pressure in dropping?

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7 Answers

Hydro Works Plumbing and Heating Services Ltd.

Rating: 4.7 out of 5
Hull
If it guaranteed there is no leak on the system the only other thing is the boiler, could possibly be a cracked heat exchanger or faulty auto air vent etc.
Answered12 January 2020
0

Anonymous user

Hi, there are couple of things to be checked: 1-pressure releasing valve 2-expansion vessel 3-automatic air vent All the radiators valves and connections I don’t recommend leak seal!!
Answered12 January 2020
0

cosy homes

Rating: 5 out of 5
Paignton
What boiler is it ? If it’s a ideal it may be the heat exchanger and you will not see a leak and it will be covered under warranty
Answered12 January 2020
0

Anonymous user

If there has been no leak found and no drop in pressure when the boiler is switched off.. the problem either is the expansion vessel or crack in main heat exchanger opening up when boiler is hot.
Answered12 January 2020
0

Sheriff Heating & Plumbing Services

Rating: 5 out of 5
Luton
If you have a leak in boiler pressure, it's mainly limited to 3 reasons. With this in mind, the leak generally shows when the system is running (system is fully pressurised and pump is on so, continuous circulation). Causes: 1. Having a leak in any of the pipe works or fittings. With underfloor heating, it's not easy to determin unless you have one of these sophisticated equipment that can show leaks under floor or, simply by process of elimination. 2. Faulty Pressure Relief Valve (PRV). 3. Expansion vessel losing pressure or its faulty. Expansion vessel should be checked and, pressure should read 1mb or 1.25mb. If the pressure from expansion vessel keeps dropping then it means the rubber diaphragm within the expansion vessel has ruptured and, it's recommended to be replaced at this point. Considering the age of the boiler, it's unlikely to be leaking heating exchanger but, please do check the pump auto vent to be 100% sure that auto vent is OK.
Answered13 January 2020
0

Msc Domestic Services

Rating: 5 out of 5
Egham
Hi I would check to see what happens with the pressure of the system when the boiler is on. May be the expansion vessel needs topping up or the PRV is letting by
Answered13 January 2020
0

Hatty's Heating Co.

Rating: 5 out of 5
Bexhill On Sea
Before putting in leak sealer I would check the expansion vessel pressure and see if the pressure relief valve is lifting.Then I would isolate the boiler from the system, increase the pressure in the boiler to 2.5 bar and leave overnight, just in case the heat exchanger is leaking. If that’s ok and with no visible leak anywhere then I would suggest that leak sealer might be the answer, preferable to digging up the floor, this would be a last resort.
Answered13 January 2020
0