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A boiler tells you most of what is wrong through two instruments: the pressure gauge and the display. Read both before you touch anything.
The direct answer: read the pressure gauge, note any error code on the display, and check whether the fault affects heating, hot water, or both — those three facts identify most boiler problems. Then call 020 4577 2888 to be connected with a local plumber and report exactly what you saw. If you smell gas at any point, skip all of this: leave the building and call 0800 111 999.
If you smell gas — near the boiler or anywhere else — leave the property, do not operate light switches or appliances and do not use naked flames. From a safe distance, call the National Gas Emergency Service on 0800 111 999. Return only when told it is safe. Every other section of this page assumes you do not smell gas. Note too that any repair touching the gas side of a boiler must legally be done by a suitably qualified engineer — it is reasonable to ask whoever attends whether they are Gas Safe registered for that work.
Cold, most sealed systems sit around 1 to 1.5 bar; your manual gives the exact band for your model. The needle position sorts the problem into one of four branches.
An error code is not decoration; it is the boiler stating its complaint in shorthand. Write it down exactly, including letters, before resetting anything.
Which service has failed is itself diagnostic — the split tells you which part of the system to suspect.
The area's stock spans Victorian terraces, post-war council-built homes and modern commuter estates, and the heating systems inside follow the same spread — from older setups with tanks and cylinders, part-modernised over the years, to recent combis on plastic pipework. When you call, say what kind of system you have as well as what it is doing: a cylinder losing its schedule and a combi losing its diverter valve produce the same cold shower for two entirely different reasons, and the right van stock differs for each.
Topping up once via the filling loop is reasonable. If the gauge falls again within days, stop topping up and have the loss traced — repeated refills add fresh water and fresh oxygen to the system, and whatever is letting the pressure out is still there.
On a combi, hot water failing while the heating runs often points to the diverter valve or a sensor rather than a dead boiler. On a system with a cylinder, check the cylinder thermostat and the timed schedule first. Either way the pattern narrows the fault usefully — describe it exactly when you call.
Once. A lockout is the boiler protecting itself, and the error code is the clue to why. If it locks out again after one reset, note the code and stop — repeated resets can mask a fault that needs a professional, and can make it harder to diagnose.
Stop treating it as a boiler fault. Leave the property, avoid switches, flames and anything that could spark, and call the National Gas Emergency Service on 0800 111 999 from a safe distance. A plumbing line is not the right first call for a suspected gas leak.
The main page — how the line works and the areas covered.
Go to home →Stopcock, taps, electrics — the sequence, in order.
Read the guide →One fixture or the whole house — the test that tells you.
Read the guide →How pricing is structured and what to ask before work starts.
Read the guide →Pressure, clock, power — the checks that find most causes.
Read the guide →Gentle thawing from the tap end back — and prevention.
Read the guide →Damp patches, dropping pressure — the test that settles it.
Read the guide →Describe what the boiler showed you and be connected with a local plumber covering Falkirk and the surrounding towns, any hour.
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