Will turning my water off affect my boiler?

A common question is whether turning off the mains water supply will damage a boiler. The good news is that no, it won’t and this concern is based on a misunderstanding. The water that circulates through your boiler is not the same as the water coming out of your taps.

The water heated by your boiler is part of a closed-loop system. This means it continuously circulates, heating and cooling as it travels through pipes, radiators, and sometimes storage cylinders, to provide warmth for your home. The water in this closed-loop is not reliant on the mains water supply to function, so turning off the supply to the taps will not affect this system.

When you turn off the water, you are only cutting off the supply to your taps and will not impact the operation of your heating system.

For combi boilers, which provide both heating and hot water, turning off the mains water supply will stop the boiler from supplying hot water. However, the heating function will still work as long as there’s no issue with the central heating circuit.

If you have a heat-only boiler (sometimes called a regular or conventional boiler) or a system boiler, turning off the water supply won’t stop your heating from working. Your radiators will continue to heat up as usual. You might still get a small amount of hot water from the cylinder, but this will quickly run out once the system loses pressure and new water isn’t able to enter the system to replace it.

If you’re considering turning off your boiler during a holiday, it’s important to think about the timing. While it’s generally safe to turn off the boiler during the warmer months, it’s advisable to keep it on during winter, especially if you’re going away for an extended period. Keeping the boiler on in winter helps to prevent freezing by maintaining frost protection. This is particularly important in colder climates, where freezing pipes can lead to serious damage.