Boiler losing pressure in Macclesfield
In short
A sealed heating system should hold its pressure for months. If yours drops week after week, water is leaving somewhere — a radiator valve, a joint, buried pipework, or out through the pressure relief valve because the expansion vessel has lost its charge. Repeated topping up is a symptom, not a maintenance task.
Also called: boiler pressure keeps dropping · topping up boiler pressure · low boiler pressure · boiler pressure too high
Signs you need this
- Pressure gauge falling below 1 bar repeatedly
- Topping up more than once or twice a year
- Boiler locking out on low pressure
- Pressure spiking well above 2.5 bar when hot
- Water dripping from the discharge pipe outside
- Rust or salt-like deposits under radiator valves
Understand what the gauge is telling you. A sealed system is filled to around 1 to 1.5 bar cold, and the pressure rises as the water heats and expands, then falls back as it cools. That daily swing is normal. What is not normal is a steady downward trend over days and weeks — that means water has left the system, because nothing else can reduce the volume.
The escape routes are a short list. Radiator valve glands weep slowly and leave a rust or salt-coloured deposit rather than a puddle. Joints in accessible pipework do the same. Automatic air vents pass. Buried pipework in a floor leaks invisibly. And the pressure relief valve discharges outside, which is why the copper pipe on the outside wall is always worth inspecting — a wet pipe or a stained wall below it is the giveaway.
The expansion vessel is the misdiagnosis that costs people money. It is a sealed chamber with an air charge on one side of a diaphragm which absorbs the expansion of heating water. Lose the air charge and there is nowhere for the expansion to go, so pressure spikes on every heat-up, discharges through the relief valve, and reads low again when cold. It looks exactly like a leak, and no amount of searching will find one. Testing the vessel's charge is a five-minute job and it should be done early, not last.
Topping up repeatedly does active harm. Every refill introduces fresh, oxygenated water into a system designed to hold the same water indefinitely, and oxygen is what corrodes the inside of steel radiators into magnetite sludge. A system topped up monthly for two years will be visibly dirtier for it.
The right sequence is: confirm the loss, inspect the visible candidates, check the discharge pipe outside, test the expansion vessel and PRV, and only then start looking at buried pipework with thermal imaging. Following that order finds most faults in one visit.
What the job covers
- Confirming and quantifying the loss with a pressure test
- Inspection of valves, joints, air vents and the external discharge
- Expansion vessel charge test, recharge or replacement
- Pressure relief valve testing and replacement
- Thermal imaging for buried heating pipework
- Refill with inhibitor once the fault is corrected
What it costs
We don't publish a price for this yet, because a number pulled out of the air is worse than no number at all — your plumber has to honour it. You'll get a firm price for your actual job when they ring you back, before any work starts. The quote itself is free and there's no obligation either way.
Common questions
Is it safe to keep topping it up?
As a short-term measure to keep the heating running, yes. As a routine, no — it damages the system through repeated oxygenation and it leaves the actual fault unfixed.
There is no leak anywhere. What now?
That pattern usually points at the expansion vessel or the pressure relief valve. Both are quick to test and far cheaper to sort than lifting floors looking for water that is not there.
Need this doing in Macclesfield?
Tell us the job and it goes straight to our local plumber — one call back, usually the same day. Free quote, no obligation.