Boiler Not Working: Where to Start

First: is anything unsafe?

If you smell gas, do not touch switches. Open windows, turn off the gas at the meter if you can, leave the property and call the National Gas Emergency Service on 0800 111 999. If water is near electrics, switch the power off at the consumer unit. Only carry on with the checks below once you are sure it is safe.

Five checks before anything else

A surprising number of call-outs come down to one of these:

• Is there power to the boiler, and is the display on?
• Is the gas on? Try the hob if you have a gas one, and check a prepayment meter has credit
• What does the pressure gauge read?
• Are the timer and thermostat asking for heat?
• Is there a fault code on the display? Write it down

Match your symptom

Find the line that best fits what you are seeing:

• Nothing happens, or it clicks and will not light: boiler not firing up
• Taps run cold: no hot water from the boiler
• Hot taps fine but radiators cold: hot water but no heating
• Pressure keeps dropping: boiler losing pressure, then how to repressurise a boiler
• Gauge in the red: boiler pressure too high
• Water under the boiler: boiler leaking water
• Banging, gurgling or whistling: boiler making noise
• Some rooms or floors cold: radiators not heating up
• Radiator warm at the top only: radiator cold at the bottom
• Drips under a radiator: radiator leaking

Why a boiler keeps turning off

A boiler that fires, runs for a few minutes and then shuts down is usually protecting itself. Low pressure, poor circulation from sludge or a sticking pump, a blocked condensate pipe or a faulty sensor can all make it overheat or lock out. A thermostat placed too close to a radiator can also switch it off early.

In freezing weather, a frozen condensate pipe is the classic cause. Pouring warm water along the outside section of the pipe and then resetting the boiler often gets it going again.

Leaks from the boiler

Boilers leak when seals perish, a pressure relief valve opens, or an internal part corrodes. Wipe the area dry, put a container underneath and find where the water appears. Never take the boiler casing off to look; leaks inside need a Gas Safe engineer. Our boiler leaking water guide explains where to look.

Need it sorted? Book a boiler repair

Write down the boiler make, any fault code and what you have tried, then call or WhatsApp 07429 632804. Read about our boiler repairs, or, if you have lost heating and hot water entirely, see emergency boiler repair. For a non-urgent fault, use the quote form.