How to Turn Off a Boiler, and Which Way Is Right for You

Which way should you turn it off?

Most people who search for this are in one of a handful of situations, and each one has a different best answer. Pick yours from the list, then read the matching step below.

• You want the heating off for summer, or the house is too warm: use the programmer or thermostat only.
• The boiler is leaking, dripping or making a noise you do not like: power button, then the fused switch, then close the cold water valve if it is a combi.
• You can smell gas or your carbon monoxide alarm is sounding: no switches, gas off at the meter, windows open, get out and call 0800 111 999.
• You are going away in winter: usually leave it on, on a low or frost setting, rather than off.
• Someone is coming to work on it: the engineer will isolate it properly, but switching it off at the fused switch beforehand does no harm.

Option 1: turn the heating and hot water off at the controls

This is the gentlest way and the one to use for anything routine. On a digital programmer, set the heating channel and the hot water channel to off. On a mechanical dial timer, push the selector to off or set every pin up. If you have a room thermostat, turning it right down stops the heating calling but does nothing to the hot water, so the programmer is the better switch.

The boiler stays powered, so its display stays lit. That is what you want. Most modern boilers have a built in frost protection function that fires the burner if the boiler itself gets close to freezing, and many also run the pump briefly now and then so it does not seize over a long idle spell. Both need power. Our guide on how to set a heating timer covers the different programmer types if yours is unfamiliar.

Option 2: the boiler's own on/off or standby button

Most boilers fitted in the last fifteen years have a power or standby button on the front panel, sometimes behind a drop down flap. On some it is marked with the standard power symbol, on others it is a dial with an off position. Pressing it shuts the burner down and blanks or dims the display.

On many models this is a standby rather than a true off, so the circuit board may still be live. Treat it as the first step before the fused switch, not as a way of making the boiler safe to open. You should never take the casing off a gas boiler yourself in any case.

Option 3: the fused switch on the wall

Every boiler is wired through a fused switch, usually a white plate with a rocker switch and a small fuse drawer, mounted on the wall or kitchen unit within a metre or so of the boiler. It may be labelled boiler or central heating. Switching it off cuts all power to the boiler, the pump and usually the controls as well.

Use it when the boiler is leaking, when water has got anywhere near the electrics, or when something is clearly wrong. If water is actually running onto the boiler or the fused switch, do not reach through water to operate it. Turn off the circuit at the consumer unit instead, and only if you can reach that without standing in water.

Remember that a boiler switched off at the wall has no frost protection. In winter, that matters if the boiler is in a garage, a loft or an outside cupboard.

If you smell gas, skip this step entirely. Operating any electrical switch, on or off, can make a spark. Go straight to the gas valve at the meter.

Option 4: turning off the gas

The emergency control valve is on the pipe next to your gas meter. It has a lever handle. When the lever lines up with the pipe the gas is on, and when it sits across the pipe the gas is off. Turn it a quarter turn so it is across the pipe. In flats the meter may be in a cupboard on the landing, in a communal meter room or outside, so it is worth finding it now rather than in the dark.

This is the step for a gas smell or a carbon monoxide alarm. After turning it off, open doors and windows, do not use light switches, doorbells or anything with a flame, get everyone outside, and call the National Gas Emergency line on 0800 111 999. Our guide on what to do if you smell gas walks through it in order. Do not turn the gas back on until the emergency engineer says it is safe, and have the boiler checked by a Gas Safe registered engineer before it is used again.

If the boiler is leaking

Switch it off at the power button, then the fused switch. On a combi, the pipes underneath include a cold mains inlet with a small valve, often a slotted quarter turn valve or a lever. Closing it stops mains water entering the boiler, which slows a leak on the hot water side. A leak from the heating side will usually stop on its own as the pressure gauge falls towards zero, because a sealed heating system holds only a small amount of water.

Put a container under the drip. If you cannot find the right valve, the main stopcock stops all mains water into the house. Our guide on water escaping covers what to do first if water has reached ceilings or lights.

If the boiler is a system or regular boiler with a hot water cylinder, switch the immersion heater on and you will usually still have hot water while the boiler is off. How to turn on an immersion heater shows where that switch lives.

Should you turn the boiler off in summer?

There is no need to switch it off at the wall. Turn the heating channel off and leave the hot water on its normal times if the boiler also heats your water. A boiler sitting on standby uses very little electricity, and keeping it powered lets the pump anti seize and frost protection functions work. Switching it off completely for months is one of the reasons boilers and valves stick when the heating goes back on in October.

If you have a combi and want it fully off while you are away in summer, switching off at the fused switch is fine. Just turn it back on and run the heating for ten minutes before the first cold week, which is the test run our when to turn the heating on guide recommends.

Going away in winter: off, or on low?

For a normal week or two away between October and March, leave the boiler on. Set the heating to frost protection or a low temperature, around 12 to 15 degrees on the thermostat if it has no frost setting. Switching the boiler off at the wall and leaving an unheated house through a cold snap is how pipes and cylinders freeze. If the boiler or any pipework is in a garage, loft or outbuilding, our guide on the frost stat explains the extra protection those spaces need.

For a long spell with nobody in the property, the safer approach is to drain the water system down, which is a job for an engineer on an unvented cylinder or a sealed heating system. Check your home insurance wording too, as some policies set conditions for empty homes in winter.

Turning it back on afterwards

Reverse the order you used. Gas back on only if you turned it off for a reason that has been dealt with. Fused switch on, then the power button, then set the programmer back to its normal times. Check the pressure gauge: on most combis and system boilers it should read somewhere around 1 to 1.5 bar when cold. If it is well below that, the boiler may refuse to fire until it is topped up. If it is well above, our guide on boiler pressure too high explains why.

If the boiler shows a fault code or will not light, pressing reset once or twice is reasonable. Pressing it over and over is not, because the boiler is telling you something. At that point, call us on 020 4652 5111 or send an enquiry with the make, the model and the code on the display. We have 20 engineers across London, and our rate is on the pricing page and agreed before we attend.