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

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

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?

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.

On Dec 25, 4:00*pm, Tim Streater wrote:
In article
,

*MM wrote:
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?

1) Why would the temperature in the room be at 0C constantly?

Why not? It was only an assumption.

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.

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


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.

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

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.
--
Bill

"Bill" wrote in message
...
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.
--
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

On Sun, 26 Dec 2010 11:22:14 +1300, "David WE Roberts"
wrote:



"Bill" wrote in message
...
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.
--
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.

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:
http://www.dealec.co.uk/acatalog/hyl...e_heaters.html

to put near the loft pipework.

MM

On Sun, 26 Dec 2010 21:22:32 +0000, Tim Streater
wrote:

In article
,
MM wrote:

On Dec 25, 4:000m, Tim Streater wrote:
In article
,


M wrote:
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?

1) Why would the temperature in the room be at 0C constantly?

Why not? It was only an assumption.

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.

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

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

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

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.

MM

In article ,
says...
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:
http://www.dealec.co.uk/acatalog/hyl...e_heaters.html

to put near the loft pipework.

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.

--
Skipweasel - never knowingly understood.

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.

On Mon, 27 Dec 2010 15:45:30 -0000, Skipweasel wrote:

In article ,
says...
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:
http://www.dealec.co.uk/acatalog/hyl...e_heaters.html

to put near the loft pipework.

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.

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

On Mon, 27 Dec 2010 17:30:21 +0000, The Natural Philosopher
wrote:

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.

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.

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.

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.

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

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

MM