The water main coming into my house comes in one of the unheated rooms connected to my house. I have insulated the room with styroboard panels and it’s currently not going below 2 degrees (I have a max/min thermometer). It’s minus 8 outside and has been kind of these temperatures most nights for the past week.
Hopefully, the cold will pass in the next few weeks.
My question is, at what temperature do pipes freeze? I know that water freezes at 0 but I would imagine that pipes need a bit colder before damage occurs. I’m just trying to work out if I need to put any heating in this room. The rest of my house is heated with wood ovens.

The water in the pipes will freeze if static and below freezing. How long it takes to get to that state depends on whether the water is flowing and external factors like air flow (cold air , e.g. Sub zero windchill) will cool the pipes more quickly than air that isn’t moving much.

If its plastic, it should be OK. If you insulate it, when it does freeze, it’ll take an age to defrost again!

If you are really worried, you can get a tape/wire that wraps around the pipe and gives off a little heat to stop the pipes freezing. Seems to start at about £6 on ebay for the dodgy Chinese/Korean stuff, £15 for something decent. They had it in the washrooms at a campsite, only noticed as the cold tap ran lukewarm for the first 20 seconds 🙂

PS Windchill doesn’t ‘exist’ if the object is already the same temperature as the wind, so won’t affect the freezing point. Unless of course, you have the above heat tape…then windchill would increase heat loss.

That mentioned above is called trace heating.
Plastic is a **** for freezing. I leave a small amount running through at work if possible as it sometimes stops it from freezing completely. This isn’t ideal if you’re on a meter obviously. Decent insulation around the pipes is what you require. As a rule tap water at this time of year is around 9 degree c as it comes through.

Iirc -6 before you need to be really worried, assumes airflow. Bear in mind the water coming out of the mains supply probably won’t be any colder than zero as you will be well below the frost line. Unless you live somewhere that stays really cold for a long time.

Wouldn’t worry if the unheated room temp isn’t well below freezing for a couple of days. Especially if the house is i use and the water isn’t sitting in the pipes. The only time I’ve ever had a frozen pipe was in the bad winter 1980-81. I got back to my tenement flat after a couple of days away. The water in the toilet pan had frozen. The lead rising main buried in the wall of the kitchen had frozen solid.

But daytime temps had been -10 for weeks. There had been hundreds of burst pipes all over Glasgow.

Edit Actually google says Dec 81 was the cold one. -13 in Glasgow.

http://www.trevorharley.com/trevorharley/weather_web_pages/british_weather_in_december.htm

Freezing isn’t the issue.

Water is unusual in that it will.start to expand from +4degrees Celsius. A little flow will decrease the pressure.

To be clear, as the temp drops it contracts to +4degrees then starts to expand until solid (unsure what supercooled water does).

Our washing machine burst a valve inside during the 2010 freeze, but the pipes were ok. That was in an untested garage. I think you’d need static water & sub zero for a good few days to have any problems.