John Rumm wrote:
On 27/12/2010 15:28, MM wrote:
On Sat, 25 Dec 2010 16:11:18 +0000, John Rumm
wrote:

On 25/12/2010 11:54, MM wrote:

I've been puzzling how modern pipe insulation works. If the

Same as old insulation, although perhaps better.

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.)

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

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

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.

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

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.

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.