No heating or no hot water: what to check before you call

When the heating or the hot water stops, a few checks from the hallway sort a setting from a breakdown. None of them involve taking the boiler case off. If the boiler is leaking, showing a yellow flame, or you can smell gas, skip the list and use the safety steps at the end.

Checks that are safe to do

• The programmer or timer is in an on period, not left on a holiday setting or a clock that has reset
• The room thermostat is turned up above the temperature of the room, and is calling for heat
• Radiator valves are open on the radiators you expect to be hot, including lockshields that have been closed for decorating
• The boiler display is on. A blank panel can be a power cut, a fused spur that was switched off, or a fault

No heating with hot water still running is a different fault from no hot water with the radiators still warming. Say which one it is when you call. A combi that has lost only the heating is not the same visit as one that has gone completely dead.

Boiler pressure

On a sealed system, the gauge or the digital display shows the pressure of the water in the radiators. A typical cold system sits around 1 to 1.5 bar. The manual for your boiler is the figure that counts, not a number from a general article. If you have just bled radiators, the pressure often drops, and the system needs topping up afterwards.

If you repressurise it yourself, switch the boiler off and let it cool first, and follow the filling loop in the manual. If you are not sure which valve is the filling loop, leave it. Pressure that falls again after it has been set, or pressure that is far too high, needs an engineer. A repeated drop is often a leak, on a radiator or on the boiler, and topping it up only hides that.

What not to open

Do not remove the boiler case, and do not attempt a repair on the gas side. A yearly service by a Gas Safe registered engineer is the usual way to catch a fault before a cold week, and it is worth doing before winter if the last one was more than twelve months ago. In a rented home, the landlord arranges the gas safety check. A service is also what keeps many manufacturers' warranties valid. We do not quote a price for that until we know the boiler.

When to stop checking and call

• The boiler locks out again after a reset
• Water is coming from the boiler or the pipes at the wall
• The flame is yellow or floppy, or there is soot or black marking
• Anyone in the house has a headache, nausea, or dizziness and an appliance may be burning badly

If you smell gas, call the National Gas Emergency Service on 0800 111 999. Where you can do so safely, turn the gas off, open windows, and keep away from switches and naked flames. Then call us on +44 7746 210558. For a breakdown with no smell of gas, call the same number, describe what has stopped, and we agree the call-out before anyone sets off. We attend the same day, 24 hours a day, across Bradford, Leeds, and the rest of West Yorkshire.