Combi boiler and mains water supply switch off

[Anotherdayattheforum]

Hi. Can you advise re my Worcester-Borsch combi boiler, what I need to be aware of if I turn my water mains supply off for a week in January?

I want to ensure that by protecting myself from an unexpected water leak, I’m not inadvertently causing damage to the boiler.

The period I plan to turn the water supply off - no freezing temperatures forecast.

I have my boiler serviced annually. Last service December 2025. All good. System pressure - no problem.

Thanks in advance.

This suggests it is OK as your boiler will have inbuilt protections. Maybe check with the person who services your boiler?

idealheating.com/tips-and-advice/will-turning-my-water-off-affect-my-boiler

You can leave the heating running at a low setting. With no water being used the pressure will not drop. It would be upsetting if you had a radiator pipe burst, and some of them run in unheated spaces like under floors. This will also keep the house dry.

My insurers require an empty house to be heated to 12C, 24 hours. This is actually very cheap, because, in England, outdoor winter temperatures are often around 5C to 10C, so very little extra heat is needed.

I presume you have no pipes or tanks in the loft. This unheated space is very prone to freezing, especially when the house is empty and there is no water flow.

We turn the water off all the time in our caravan when empty, no issues with the combi boiler although there is antifreeze in in the system.
Make sure you put it on the frost setting (check instruction booklet or online for your model) to avoid frozen pipes, as despite the forecast you don't want a disaster.

Really helpful. Thank you all.