Gas Boiler Service and Repair

What we check on a gas boiler service

Burning gas safely. We check the flue and the terminal outside, then use a flue gas analyser to see whether the boiler is burning cleanly or producing too much carbon monoxide.

Gas and safety devices. We test the gas pressure and the devices that shut the boiler down in a fault.

Inside the case. We inspect the burner, heat exchanger, fan, electrodes and seals, cleaning where the manufacturer asks, and clear the condensate trap, a common cause of lockouts.

The system around it. We check the pressure, expansion vessel, pump and controls, and clean the magnetic filter if one is fitted.

Common boiler faults and what they usually mean

The pressure keeps dropping. Most sealed systems sit at around 1 to 1.5 bar when cold. If you keep topping it up, water is escaping, often from a leak, the pressure relief valve or a tired expansion vessel.

Heating works but there's no hot water. On a combi boiler this often points to the diverting valve. With a cylinder, check the timer first.

The boiler locks out in freezing weather. The condensate pipe outside can freeze and block. Pouring warm, not boiling, water over the frozen section often clears it.

A fault code on the display. Write the code down before you reset anything. It tells the engineer where to start.

Before you book, check the gas and electricity are on and the thermostat is asking for heat. If the boiler still won't run, don't keep resetting it.

What affects the cost of a boiler repair or service

We price each repair once we know what has failed. The cost depends on:

The fault itself. Re-pressurising the system or clearing a blocked condensate pipe is a small job. A failed fan, pump, diverting valve or circuit board costs more.

Parts. Parts for older or less common boilers can take longer to arrive and cost more.

The cost of a yearly service depends on the make and model, how easy the boiler is to reach and whether other gas appliances need checking.

Repair, replace or plan for what comes next

If your boiler is well into its second decade, repairs start to add up. If a new boiler makes more sense, see our gas boiler installation service.

If you're thinking about moving away from gas one day, we can look at whether your home would suit a heat pump, with no pressure to change before you're ready. Our air source heat pumps page explains how we design and fit them, and our guide to the Boiler Upgrade Scheme covers the grant towards the cost.