How much does it take to freeze pipes?

My house in Scotland is unoccupied. It's obviously not the best idea for me to get in the car and drive up there at the moment (though I will between xmas and new year if I get a few days break in the weather).

The house is a detached timber framed bungalow, with a concrete base, then a timber frame sitting on top, with a chipboard floor suspended on the frame, about 2" off the concrete base.

All the pipes for water and central heating run in this two inch void, underneath the floor.

The central heating should be on for 15 minutes at 6 hour intervals (midnight 6am, midday, 6pm), assuming the boiler has been firing up properly for the past 6 weeks since I was up there.

Scotland has been seeing temperatures as low as -15.

I would send a key to someone up there to go and check it, but mail is not getting through and I could probably get up there myself before the key arrived. I will definitely be leaving a set of keys with Kilted Ginger next time I am up there. I don't really know any of the neighbours well enough to leave keys with them.

Do you think the house will be OK?

[timwilky]

I think you may have problems.

When I moved in here years ago, the central heating was off in one unused bedroom, that burst despite the room underneath being heated.

[G]

In answer to How much does it take to freeze pipes?... Temperatures below 0c

If the house is well insulated and double glazed I cant see internal temps reaching below freezing

The overflow pipe/condensation pipe seems to be the biggest problem around our area (-10 recently). They freeze up and the boiler can't fire up, or something like that.

Not had a problem myself though.

The central heating SHOULD be on in every room (every radiator was warming up was when I left it).

Originally Posted by G

In answer to How much does it take to freeze pipes?... Temperatures below 0c

But is 6 hours between hot water flowing through the pipe enough to let it freeze before it gets another flow of hot water? Ice obviously doesn't just suddenly happen. It crystallises and forms slowly at 0 degrees, and the process gets faster as the temperature drops below freezing. If you put kids ice pops in your freezer, they take a few hours to freeze solid, they are about the same diameter as a pipe, but obviously much less well protected and in a freezer.

The house is 6 years old, so well double glazed and insulated, then of course the pipes themselves are lagged. If internal temperatures are getting below freezing, then I guess my worry is six hours without heat enough to burst a pipe? My other worry is something like G says, if the boiler has packed in with the low temperatures and the house is getting no heat at all.

[andrewsmith]

all being well, your boiler cycle will keep the pipes from freezing.

I'd definitely try and keep a set of key local incase something does go pete tong

[G]

Alternatively if its unoccupied for any duration (like it appears to be) switch off the water and drain the system to remove all risk and worry.

It will only take a turn of the the stop lock and 5 minutes to fill the system again next time your there or get a tenant moving in.

Originally Posted by G

Alternatively if its unoccupied for any duration (like it appears to be) switch off the water and drain the system to remove all risk and worry.

It will only take a turn of the the stop lock and 5 minutes to fill the system again next time your there or get a tenant moving in.

How do I go about that? Would I need to bleed all the radiators again afterwards?

Your boiler should have a bleed out valve to allow the system to be flushed, the lowest radiator in the house should have also been fitted with a skirting board level bleed valve. For the other pipes running under the floor (nearly all yours seen as its a bungalow) I have no idea how you empty these maybe its got a removable end cap on one of the pipes maybe where it goes underground after it exists the boiler.

Thats total speculation though, but FREE BUMP

[G]

Originally Posted by -Ralph-

How do I go about that? Would I need to bleed all the radiators again afterwards?

You would need to drain each radiator, the expansion tank/boiler and water tank in the loft. When I helped replace the radiators in a friend’s house we used a DIY book I have, but it was really straight forwards anyway. Literally turn off the power to the system, turn off the water, secure the ball valve in your tank and drain with a hosepipe etc.

You will need to bleed all the radiators when you refill the system though. Starting downstairs, then working your way up. It shouldn't take you that long unless it's a beast of a house probably a little longer than 5 minutes I guess in most cases.

If you’re out of the property for the whole of winter or longer it would be worth it though for peace of mind. Beats paying robbing companies for gas and electricity to heat the place when your not there. The most energy is used when the boiler starts up every time.

[Luckypants]

Originally Posted by -Ralph-

How do I go about that? Would I need to bleed all the radiators again afterwards?

As the house is quite modern, AFAIK building regs require that a drain <male hen word> that allows the entire system to be drained is fitted. This is often on an outside wall below the level of the underfloor pipes. Go take a look.

Refill is probably as straightforward as suggested if it is a vented system. If it is a pressurised system I think (but do not know) that the boiler will need recommissioning.

As an aside, if you told your insurers that the property is not occupied, they will have told you to drain the system (probably in the small print). They certainly told us to do it when we told them my mum's place is now empty. If you have had a burst they may not cover you if they expect you to have drained the system. Sorry to be the bearer of bad news.