Central heating
Hi, currently looking after my elderly mother’s house which is unoccupied for large periods of time. The building insurance has asked us to leave the heating on via a timer which is no probs. However we usually turn the water mains off when there is no one about so what I would like to know will the hearing etc work if I turn the water off or do I need to leave it on? Thank you.
Advice from 3 local tradespeople
You can turn it off, I would also recommend that you leave the heating on 24hrs, but turn the thermostat down to about 15° or if it's a manual thermostat then a couple of degrees under the clicking sound. That clicking sound is the ambient temperature of the stat.
So if we have a cold spell, the heating will turn on, and protect your property from frozen pipes ect.
???? Will the heating still work if the water mains is turned off?
? Yes – in most cases, the central heating system will continue to function even with the mains water turned off, as long as:
1. The boiler and heating system are sealed (pressurised combi or sealed system boiler), and
2. The system is already full of water and holding pressure before you turn off the mains.
???? Here’s how it works:
• Modern boilers (combi or system) operate using the water already inside the heating loop (radiators and pipework), not a continuous supply from the mains.
• The mains is only needed to top up pressure in sealed systems — which you’ve already done after bleeding.
• So, turning off the mains will not stop your heating from running on its timer — it will circulate the existing water through the system.
?? Exceptions / Things to Check:
1. Open-Vented System (with loft tanks)
• If the property has an older boiler with a feed-and-expansion tank in the loft, it relies on the mains to keep that tank topped up.
• Turning the mains off could eventually result in air ingress or system drain-down over time.
2. Frost Protection & Leaks
• If a leak develops while the heating runs and the pressure drops, you won’t be able to repressurize the system with the water mains off.
• In winter, if your system relies on frost protection, make sure some flow is possible and that the boiler won’t fault due to low pressure.
? Best Practice for Unoccupied Homes:
• Turn off the mains at the internal stopcock, but consider installing an auto-stop leak valve or leak detection system for extra peace of mind.
• Leave the heating on a timer or frost setting, and check that system pressure is good before leaving.
• If you’re unsure whether the system is sealed or open-vented, look for:
• A pressure gauge near the boiler = sealed system
• A small storage tank in the loft = open-vented (needs water on)
Let me know your boiler model or if you’re unsure about the system type — I’ll help you confirm.
no thats fine heating is a sealed system so turning the water off will not affect the heating system
