Outside water pipes and freezing...

Jan 20, 2021 Last reply: 5 years ago 9 Replies

We've a 15mm plastic mains water pipe on an outside wall.



I haven't got around to lagging it yet so as a precaution i've been turning it's supply off in the evening and had been expecting to open it up and find it frozen.



Having had no bother and it being zero and under recently around these parts i'm wondering at what sort of temperature you'd actually get freezing?



I realise that rather than debating this, a better use of my time would be to go and get some lagging! :)


below zero with no flow and wind.

I had a radiator freeze INSIDE a cottage once

R D S pretended :

Any temperature sub-zero is cold enough, but it also depends on how long it it below zero.

It is generally a combination of temperature and wind speed that does it. Metal pipes being somewhat more prone to it IME. How fast the heat gets out of the water determines whether it freezes or not.

It is actually quite mild today 9C but the road is running like a river.

However MDPE (black or blue) seems to be quite OK when frozen, we have quite a bit of exposed MDPE pipe outside and it has been frozen and thawed quite a few times over the years with no apparent ill effects. (It feeds a couple of horse waterers so temporary blockage doesn't matter)

The important point is that water expands as it freezes and exerts considerable force whilst doing so. MDPE pipe is flexible and accommodates this, copper does not and splits or maybe forces open a compression joint. Of course you don't know about this until the water thaws.

Yes, of course, I thought the OP's original message indicated that the pipework in question was mostly MDPE. Our outside MDPE pipework has metal 'endings' as it were and these have always survived OK. There's a standpipe style tap at one point and two pretty standard ball float valves in the horse waterers. These have survived many years of occasional freezing.

Even lagging is not always enough. During that big freeze in 63, pipes underground were freezing. A little messy when the thaw came. Brian

Yes wind chill will be the thing. If its sheltered water does not always freeze all the way through the pipe. Brian

One thing to beware of with non-bursting pipes freezing, is the danger of an ice blockage ...

When we moved into our current place, the outlet from the washing machine went outside and under the back doorstep to the gutter drain in the back yard. It was generally out of sight out of mind, until it froze in 2010, and the washing machine *almost* flooded the house. Luckily I had fitted a small sink in the cloakroom next door and had borrowed that pipe run for the waste. Went to use the cloakroom, briefly wondered why the sink wouldn't empty then twigged just before the washing machine emptied :)

Tackling the blockage eventually yielded a yard-long spear of ice from the pipe.

After that I replumbed all the wastes into an adaptor that goes into the toilet coupling. All nice and warm indoors now.

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