On Wed, 07 Oct 2020 20:56:10 +0100 (BST), "Dave Liquorice"
wrote:

snip

Or all of the pipe work above the tap in question. If air can get in
water can get out.

A mate, bought a fixer upper and had quite a bit of the place open mid
winter so got the coal fire (/ direct back boiler) going hard one
evening till he heard some strange rumbling noises from upstairs and
found the water boiling in the cylinder.

He damped the fire down and went to bed.

The next morning he ran some hot water off and it ran for a while then
slowed as he heard some different noises from upstairs and went into
the bathroom to find the HWC collapsed like an old beer can!

Upon inspection the cold feed from the cold water tank had frozen
solid, as had the expansion pipe (after water had boiled over),
cutting the supply of water or air and the resultant collapse.

He then soldered bits of pipe to the cylinder as handles to pull most
of the dents out then soldered up any splits, just to tide him over.
;-(

I would be surprised if he is still with us as when wiring the same
house he fitted a light switch, rose, drop cord and pendant ... and
when he put the lamp in it came on! Might the wooden step ladders have
saved him? ;-(

He was actually a watchmaker by trade. ;-)

Cheers, T i m