Boiler repair and breakdowns

Boiler repairs: the faults we see, and what they mean

Losing pressure

A sealed system should hold its pressure indefinitely. If the gauge drops and you top it up every few weeks, water is leaving the system somewhere, or the expansion vessel has failed.

Visible leaks are the easy case — a weeping joint, a radiator valve gland, a pinhole in pipework under a floor. Less obvious is a failed expansion vessel. The vessel absorbs the expansion of heated water; when its internal charge is lost, pressure spikes on every heating cycle, the pressure relief valve lifts, and water discharges outside through a small copper pipe. The symptom is a slow pressure loss with no leak anywhere indoors. Recharging or replacing the vessel fixes it; topping up the pressure forever does not.

No hot water but heating works, or the reverse

In a combi this nearly always points at the diverter valve, which switches flow between the heating circuit and the hot water exchanger. The mechanism sticks with age and scale. It is a very common fault in hard water areas and an entirely repairable one.

Banging, kettling and gurgling

Kettling — a noise like a kettle boiling — happens when limescale or sludge insulates parts of the heat exchanger so localised water boils. Given Surrey's hard water this is common, and it is a warning: a fouled exchanger is working harder than it should and will eventually fail.

Gurgling generally means air in the system or, in a combi, a circulation problem. Banging on start-up often points at a sticking pump or trapped air.

Fault codes and lockouts

Modern boilers report faults as codes on the display. They are manufacturer specific and they narrow the diagnosis enormously. Tell us the code when you ring and we can often bring the right part first time rather than making two visits.

A lockout after a cold night is very often a frozen condensate pipe — the condensate has nowhere to go, the boiler detects it and shuts down safely. Thawing the pipe restores operation, and insulating or resizing it prevents a repeat. It is the single most common winter call-out in the country.

Ignition failure

Repeated failure to light points at the ignition electrode, the gas valve, the flame sensing circuit or, occasionally, gas supply pressure. These are different jobs with different costs, which is why we diagnose rather than quote down the phone.

How we price it

There is no call-out charge. We charge a diagnosis fee, quoted to you before we set off, and if we carry out the repair on the same visit that fee comes off the bill. You are told what is wrong and what it costs before any work begins.

Repair or replace: the honest arithmetic

We will tell you when to stop spending, because nobody benefits from money poured into a dying boiler.

The factors are age, the cost of the repair, and parts availability. Under eight years old, repair almost always makes sense. Between eight and twelve, it depends on the part — a diverter valve is worth doing, a heat exchanger usually is not. Past twelve years, with a major component failed and parts becoming scarce, replacement is normally the better answer, and a modern boiler will be meaningfully cheaper to run.

The other consideration is whether the boiler has a guarantee left. If it does, the repair may cost you nothing, and we will tell you to claim rather than pay us.

What to do before we arrive

If there is a water leak, turn off the stopcock. If water is near electrics, switch off at the consumer unit. Note the fault code if there is one. Check the pressure gauge and tell us the reading. And if you smell gas at any point, ring the National Gas Emergency Service on 0800 111 999 first, turn the gas off at the meter if you can reach it safely, open windows, leave the electrics alone and get everyone out.