Common faults and what usually causes them

The boiler is showing a fault code

A fault code tells you which system is complaining, not which part has failed. A low pressure code can mean a flat expansion vessel, a pressure relief valve passing water, a blocked filter or a slow leak under a floor. Replacing the part the code appears to name is the most common way to spend money and still have the fault. We read the code, then test the system behind it.

Heating works but there is no hot water

On a combi boiler this usually points at the diverter valve, which decides whether heated water goes to the radiators or the taps. When it sticks on the heating side you get warm radiators and cold taps. It is a common failure and repairable on most boilers.

The boiler keeps losing pressure

Three separate faults produce this symptom and they cost very different amounts to put right. A flat expansion vessel can usually be recharged. A pressure relief valve passing water shows as a drip from the discharge pipe outside. A leak in the pipework has to be found before anything is replaced. Topping the system up every week is not a fix, and a boiler run at low pressure will lock out eventually.

Banging, kettling or gurgling

Noise from the boiler usually means the heat exchanger is dirty rather than failing. Sludge and limescale create hot spots, water boils against them, and you hear it. A new boiler fitted to the same dirty system will do the same thing within a year or two, so we check the system water before anyone starts talking about replacement. A power flush is often the answer.

The boiler stops working in cold weather

A frozen condensate pipe is the most common January call out in London. The condensate pipe runs outside, freezes, backs up, and the boiler shuts itself down. Many of these clear without an engineer by warming the external pipe with hot water, not boiling. Call us first and we will talk you through it rather than charge you for a visit you do not need.

The boiler fires up then cuts out

Short cycling points at flow rather than ignition. A blocked filter, a failing pump, a closed valve or air in the system all stop heat leaving the boiler quickly enough, so it hits temperature in seconds and shuts off. The fault is usually in the system rather than the boiler.

How we diagnose a fault

Every visit starts with the same four checks whatever the symptom: gas working pressure at the appliance, combustion readings on the flue analyser, system pressure, and the condition of the system water. Those tell us whether we are looking at a boiler fault or a system fault, which is what stops an engineer replacing a part that was never the problem.

What it costs

The call out is £150 including VAT. All our rates are published on the rates page.

If a part is needed we quote before ordering it, and we fit nothing chargeable without telling you the price first.

When a repair stops being worth doing

We will tell you when to stop spending. A boiler past twelve years old that needs a heat exchanger or a gas valve, with parts on long lead times, is usually money going into a machine near the end of its life. When that happens we price the repair and a replacement side by side and leave the decision with you.

Plenty of repairs are worth doing, and we say so when they are.

Vaillant and Baxi

We are a Vaillant specialist and a Baxi approved installer. We carry common parts for both and can work on boilers still inside their manufacturer guarantee without affecting it. On boilers we install, that guarantee runs up to 10 years provided the boiler is serviced every year and the record is signed.

Out of hours

The office line is open 8am to 5pm Monday to Friday on 020 3764 2713. For breakdowns outside those hours, see 24 hour emergency service.

Landlords and managing agents

A tenant with no heating or hot water is a repair obligation with a clock running on it. We work with property managers across London on both reactive and scheduled work, and we can carry out a gas safety certificate on the same visit where one is due.

Related services

We also handle boiler service, boiler fault finding, boiler installation and 247 emergency plumber across London.