On 5 Dec, 10:26, "DavidM" wrote:
"Heliotrope Smith" wrote in message

...



"A.Lee" wrote in message
.. .
I need to drain down a hot water system soon to fit a new sink (no stop
cocks at all on the hot water side).
To save time, would buying one of the £9ish pipe freezing sprays work
for the 5 - 10 minutes that the 15mm pipe is likely to be open while an
isolator is fitted?
If so, then it could save me a hour waiting for the drain down.
Thanks
Alan.

No need to go to the expense of freezer for this job.

If there is no isolator from cold tank to cylinder (unusual) then just
make
up a bung, roll up your sleeve and insert it into the cold outlet to the
cylinder inside the tank. Open hot tap at sink and hot tap upstairs to
drain
off pipework and cut and fix isolator. Cost? Nil. Time? A few minutes.

Some long time ago (years) I read (I think on this group) a warning
about this method, that it could cause the HW cylinder to collapse.
Presumably closing the inlet to the cylinder, and then opening a
downstairs tap causes some negative pressure to build up somewhere
to prevent the cylinder draining. Maybe cylinders are stronger these
day? Am I talking complete cobblers?

Back on subject - I've used these freezer sprays many time, on hot
and cold water supplies and central heating pipes. Make sure there's
no water running through the pipe (it won't freeze) and that any hot
water pipes have completely cooled. If soldering the pipe keep at
least 18 inches away from frozen bit, or clip a mole wrench around
the pipe to conduct some of the heat away - and solder quickly!

When finished retain the foam jacket and plastic nozzle from the
can - you can re use them and just buy new cans of freezer spray,
cheaper than a complete kit!

David

A word of extra advice: Make sure you hold the spray can in a vertical
orientation, otherwise it can discharge without actually freezing
anything. I speak from bitter experience.
Use freezer spray sideways - can empties - pipe seems cold
Cut pipe - water everywhere
PANIC - look for towels - run to garage to find second can of freezer
spray - thumb over end of pipe
Discharge second can in correct orientation
Take thumb off - no water - ecstatic joy!
That was a *bad* plumbing experience.

Jon.