At what outside temperature could the pipes freeze? Can we get away with this…

[Skytheo]

We are midlands.. going away for 4 nights on Saturday and wondering whether we can leave the heating off! We don’t have a fancy system and so would prefer to just switch it off.

I wouldn't if it's going to be below freezing.

I would turn the thermostat down but leave the heating on, so it's not as warm as you'd have it if you were home, but is warm enough to keep it from getting damp or freezing if there's a cold snap

It's not due to get down to 0 before the end of the 10 day forecast (in the Midlands). It needs to be below 0 for a while for the pipes to actually freeze. And wherever your pipes are will be warmer than outside anyway, even if only a couple of degrees. So I can't imagine for a moment that your pipes will freeze. Unless you've seen another forecast where it says there are going to be periods of time where the temperature will drop below 0.

Thanks @BuzzieLittleBee . Where have you seen minis temperatures in ten days?

the one I’m looking at shows it could get down to 2 degrees but no lower for the next week…do you reckon that’s ok?

Of course it's fine! Water freezes at 0c, so if it doesn't get that cold, it can't freeze. And it doesn't turn to ice the minute the outside temp drops to 0.

If it doesn't get lower than 2c, it is impossible for your pipes to freeze.

Water cannot freeze above its freezing point, which is 0C so it is not forecast to go below that then you don’t have a problem. To get burst pipes it needs to be below zero for quite a long time.

@Biggash the tank and boiler are in the garage. Not sure if there are pipes in the loft as I’ve never been up there (it’s my home but just got storage up there and now can’t access it as don’t have a ladder). People sometimes say flats have frozen pipes so I don’t really understand why the loft is relevant? (Not saying I don’t believe you, just don’t understand it! 😂😅)

It's relatively mild for the time of year.

If you're that worried, turn the thermostat down to, say, 15 deg. so that the heating will come of if it gets really cold. It's unlikely to kick in at all.

Technically water starts to freeze at 4°C and finishes freezing at 0°C, which is why boiler frost protection starts at 5°C normally and fridges are typically set around 4°C so they don't ice inside.

But even when it below freezing overnight, even without heating and windows open I only get down to about 8 or 9 inside. So even in the loft if the pipes are lagged it will take a long time in below freezing conditions to have a problem.

Some water systems have a cold water tank up in the loft. Lofts usually have their floor insulated, so are colder than the house - although it you do have a tank in the loft you should run the insulation over it rather than under it. Hence a PP's comment that your pipes are more in danger if there are some i the loft.

It's going to get pretty cold over New Year - can't you just leave it on 7 or something? That's our system default if it's not actually doing anything, as such.

Even if the pipes are in the loft, if the temperature isn’t below zero, they won’t freeze. What you need to do is check the weather forecast carefully.

Our frost protection thing on the thermostat is 5 degrees. Lowest I've ever seen the house get is 8 degrees, and that's when it was -8 outside

@Biggash I don’t know what the temperature is in the garage… the thermostat is by the front door. I feel really conflicted as to what to do now. There’s a big tank of water (condenser?) in the garage as well as the boiler. I remember once the small overflow pipe coming out of the garage etc had frozen but that was when it was much colder than now

It has to be sustained low temperatures, it's going to be around about 8 in the day and not less than 0 at night.

I'm also in the Midlands, a number of our water pipes are external. It causes endless problems but freezing pipes isn't one of them. Unless we start getting temperatures around -7°c, I don't worry and even if the temperature gets that low, I put one of those insulated pool noodle things over them.

You'll be absolutely fine

We have an empty probate house. We only put the heating on if it’s going to be really cold, otherwise just a couple of hours a week. We are in a cold, damp, exposed corner of the Pennines. It will be fine.

Does anyone know if Nest heating has automatic kick in function even if the system is off?

My dad sold central heating in the 1970s/1980s his advice has always been to have the heating come on in the small hours for an hour or so.

That's because it is usually the coldest at 2am or 3am.

If you have a Nest, just programme it on the frost protection setting or holiday mode, or set the temperature to something between 5 and 15 C and the heating won't come on unless the temperature drops hugely from how it is now as its really mild for December so it won't come on but also no risk of pipes freezing. No need to turn the boiler off.

Usually pipes freeze when you have a long session of well below freezing for a few nights and not above about 4 in the day, forecast is not that for the next week or so. Our condensate pipe froze in 2023 when we had that spell of very cold for about a week, I think it went down to about -10 but that pipe can freeze even if you have your heating on for some hours of the day and off at night.