emergency
Boiler losing pressure — Same-Day Plumber Across the North West
We’ll trace why your boiler is losing pressure and help get your heating steady again.
In short
A boiler losing pressure usually points to a leak, a faulty pressure relief valve, expansion vessel issues or recent bleeding of radiators. KJ Plumbers can arrange a £50 diagnostic visit in the North West, then a vetted subcontractor provides a written fixed-price quote for any repair needed.
Tell KJ what's wrong
Free and no obligation — we'll get a qualified local plumber on it.
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Hi, I'm KJ — honest UK plumbing advice, free, and a local plumber when you need one. Tell me what's happening — leak, blockage, boiler, emergency, anything — and I'll help you sort it.
You can send a photo, short video, voice note or share your location — whatever's easiest. Please avoid sending faces, documents, house numbers or payment cards in photos.
For genuine emergencies call 01706 318200, or the National Gas Emergency Service on 0800 111 999.
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Immediate steps to keep you safe
Do not keep topping it up repeatedly
Topping up once may restore heating temporarily, but regular pressure loss means something is wrong. Repeatedly adding water can dilute inhibitor, increase corrosion risk and hide an active leak.
Check for visible leaks carefully
Look around radiators, valves, pipework, the boiler casing area and the overflow pipe outside. Do not remove the boiler cover, as internal checks should only be carried out by a suitably qualified engineer.
Switch off if you see water near electrics
If water is dripping near sockets, switches or the boiler’s electrical controls, turn the appliance off and avoid touching wet electrical areas. Arrange a professional visit before using the system again.
Do not ignore sudden pressure drops
A fast drop to zero can indicate a significant leak or a safety component discharging. If the boiler will not hold pressure, stop using it and book a diagnostic rather than forcing it to run.
Common causes
What's usually behind boiler losing pressure
Small leaks on radiators or pipework
Even a tiny weep from a radiator valve, joint or hidden pipe can make boiler pressure fall over hours or days. These leaks are not always obvious, especially under floors or behind boxing.
Pressure relief valve passing water
If the pressure relief valve has opened or is not sealing properly, water may discharge through the copper pipe outside. This often leaves the boiler dropping pressure after heating up.
Expansion vessel fault
The expansion vessel absorbs the increase in water volume as the system heats. If it has lost charge or failed internally, pressure can rise too high when hot and then fall once water is released.
Air in the heating system
After radiators have been bled, the pressure can drop because air has been removed from the sealed system. If the pressure continues falling afterwards, there may be a leak or another underlying fault.
Faulty filling loop or valves
A filling loop that does not close properly can cause pressure changes, while damaged valves may weep slowly. The engineer will check whether the filling components are secure and operating correctly.
Internal boiler leak
Some pressure loss comes from components inside the boiler, such as seals, heat exchanger connections or automatic air vents. These checks must be carried out by a qualified boiler engineer.
How KJ handles this
What happens when we're on-site
- 1
Pressure history and symptom check
The vetted subcontractor will ask how often the boiler loses pressure, whether it happens hot or cold, and whether you have recently bled radiators or topped up the system.
- 2
Visual inspection of the heating system
Radiators, visible pipework, valves, towel rails and the boiler area are checked for signs of staining, corrosion, damp patches or slow weeps.
- 3
Boiler safety and component checks
Where appropriate, the engineer checks key boiler components linked to pressure loss, including the pressure relief valve route, expansion vessel behaviour and any visible internal leaks.
- 4
System pressure testing where suitable
If the fault is not immediately visible, the engineer may recommend pressure testing or further leak tracing steps to narrow down whether the issue is with the boiler, pipework or radiators.
- 5
Clear explanation of findings
You will be told what has been found, what it means, and whether the issue appears urgent, repairable on the day, or likely to need parts or further investigation.
- 6
Written fixed-price repair quote
After the £50 diagnostic visit, the engineer provides a written fixed-price quote for any repair. You can then decide whether to go ahead with the recommended work.
Where we cover
North West England — same-day where possible
FAQ
Frequent questions
Why does my boiler keep losing pressure?
Common reasons include a leak on the heating system, a pressure relief valve discharging, an expansion vessel problem, air being removed after radiator bleeding or an internal boiler leak. A diagnostic visit helps identify which cause applies in your home.
Is it safe to use a boiler that is losing pressure?
If the pressure drops slowly and the boiler is otherwise working normally, it may run for a short time after being topped up correctly. If it drops quickly, reaches zero, shows a fault code or you see water leaking, switch it off and arrange an engineer visit.
How much is the diagnostic visit?
The standard diagnostic fee is £50. This covers an engineer visit to assess the pressure loss, after which the vetted subcontractor provides a written fixed-price quote for any repair required.
Can I just top up the pressure myself?
You can usually top up a sealed heating system if you are confident using the filling loop and your boiler manual explains the process. However, if you need to do this repeatedly, there is an underlying problem that should be checked.
What pressure should my boiler be at?
Many domestic boilers sit around 1.0 to 1.5 bar when cold, but the correct range depends on the model. If pressure rises too high when heating is on and then drops afterwards, that can point towards an expansion vessel or relief valve issue.
Will you find hidden leaks under floors?
The first visit focuses on diagnosing the likely source of pressure loss from visible checks, boiler checks and system behaviour. If a hidden pipe leak is suspected, the engineer will explain the next tracing options before any further work is agreed.
Do KJ Plumbers cover my area?
KJ Plumbers helps customers across the North West of England. Share your postcode and the pressure loss symptoms, and we’ll let you know the next available diagnostic appointment.
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Tell KJ what's happening and get a plan in seconds.
Photos, video and voice notes welcome. Vetted local engineers · no call-out fee · written quote before any repair.