How does the foam rubber pipe insulation do its job?

I've been puzzling how modern pipe insulation works. If the temperature in a room is constantly at 0 dec C, then surely EVERYthing in the room - pipework, insulation etc - is at the same temperature? (Given that there is no hot water flowing through the pipes.)

So what actually does the foam insulation around pipes do to protect them?

MM

Reply to
MM
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember MM saying something like:

All insulation can do is slow down heat transfer, so a pipe in the situation you describe, with no flow of water, will eventually fall to

0degC too, and lower, if the room temp goes down. All it does is buy time until temps rise again or water flows before freezing. No magic involved.
Reply to
Grimly Curmudgeon

1) Why would the temperature in the room be at 0C constantly? 2) Water flowing through the pipes will be hotter than that, and the insulation thus prevents heat loss in the situation that the room is in fact at a low temperature.

Our boiler, for reasons bets known to itself, is in a sort of air-leaky single-glazed boot room off the back of the house. There are 28mm pipes going up to the hot tank / 3-way vale gubbins upstairs and 22mm central heating pipes coming back down. I realise that on a cold winter's night these pipes may freeze, so I'm gonna insulate them as soon as Xmas is over [1], using the 25mm stuff people have been talking about. Hopefully, the heat conducted along the copper pipe *under* the insulation, from upstairs where its warm, will keep the pipes warm even if it drops below freezing in the boot room jobby.

[1] Yes yes, I know, I know, I should have done it before. It only just struck me that I'm prolly losing a fair bit of heat out of these pipes, the runs are quite long.
Reply to
Tim Streater

Same as old insulation, although perhaps better.

Indeed - given time the whole lot would find equilibrium at the same temperature.

Well the ground water will be coming in cold, but not freezing - probably around 5 degrees C. So as long as there is some flow from time to time, the insulation will help keep the pipe above freezing.

Reply to
John Rumm

Why not? It was only an assumption.

I couldn't care less about *hot* water pipes. It's the cold ones that worry me.

I saw some heated wrap for pipes on a website earlier. Apparently you wrap it around the pipes spiral-wise and connect it to something or other? (Transformer?) and it keeps the pipes from freezing.

MM

Reply to
MM

Last night, after any reliable plumber had downed his last pint, son in law called to say there was a leak from below his outside tap through the insulation on the pipe. Turned off water in house, still gushed.

Got son as well, pulled the foam insulation back and the 3 of us assembled a hose and turned on the tap to relieve the pressure and then bound the split with gaffer tape and 3 hose clips.

It did occur to me at the time that the insulation would only be of any use if you were watering the garden at midnight in the deep midwinter.

Reply to
Bill

This is why you are supposed to:

(1) Have a stop tap inside the house between the main water system and the outside tap (2) Turn off the stop tap and open the outside tap before the onset of freezing weather.

As stated elsewhere insulation is not magic - it will stop a water pipe freezing if there is a reasonably short temperature cycle between below and above freezing but eventually the pipe will reach equilibrium with the surrounding temperature.

This is one reason to leave central heating on 'tickover' if you leave the house for a while in winter. If you don't (and don't drain the water) eventually something will freeze up in a protracted spell of sub-zero temperatures.

Cheers

Dave R

Reply to
David WE Roberts

What makes you think I was talking about hot water? I just said that water flowing through the pipes will be hotter than that.

Reply to
Tim Streater

I've just returned from 6 days away and the temperature in the loft is

+5 deg C. I left the loft hatch open and programmed the CH and hot water to come on every few hours. I also left the doors to the bedrooms ajar.

However, I'm also going to get one of these:

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put near the loft pipework.

MM

Reply to
MM

You're talking about a temperature differential of around 3 deg C as "hotter", I suppose? Anglian Water have been saying they've never experienced such low temperatures of their piped water as this December. However, no water is flowing while I'm away. Maybe it's a good idea to turn on some taps a little so that the water in the house is not static for long periods.

MM

Reply to
MM

When I'm away there's no one to turn on the taps! Nothing flows.

MM

Reply to
MM

Couldn't you just frame over it and them put the loft insulation over the frame instead of under the pipes? That way the heat from the house would keep them frost-free, but without losing that heat to the birds' feet.

Reply to
Skipweasel

If you are going to be away for any time, and can't reliably ensure the space will get enough heat to prevent freezing, this its probably better to turn the cold supply off at the stopcock, then run a tap to drop the pressure a bit and allow a little air into the pipework.

Reply to
John Rumm

The cost of a tap left dripping in a house left heated to 5-10C is well less than the cost of burst pipes and plumbers calling.

with modern cisterns with integral overflow a bit of adjustment may cause the cistern to overflow constantly, maintaining some throughput to the water system.

Reply to
The Natural Philosopher

I want backup! After the past few days of constant worry over the pipes while 150 miles away, I don't want a Christmas like that again. But yes, I'm willing to look at your suggestion in more detail. What I want is for the pipes to be *safe* from frost while minimising space heating given the 65% rise in heating oil since August.

MM

Reply to
MM

Several people suggested turning off the stopcock, but I was concerned whether the CH might fail if it "realised" there was no cold water. I don't know enough about modern CH systems to know whether one can turn off the stopcock willy nilly.

Yes, the scenario I was building in my head was to return to find the fire brigade had broken in to switch off the water and pumping out several hundred gallons. I read in the paper about a couple who came back to find their house ruined. The insurance pay-out was massive.

Good idea. I recently had to replace both ball valves and had to fine-tune the adjusting screw to stop trickle when full.

MM

Reply to
MM

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