"Andy Hall" wrote in message
news
On Fri, 26 Nov 2004 23:35:57 -0000, "IMM" wrote:


"Andy Hall" wrote in message
news
IMM wrote:

I would certainly fit an anti-vacuum
valve on the top of the cylinder.

You don't even know what an anti-vacuum valve is.

http://www.rwc.co.uk/rwc/pdfs/hcv/antivac.pdf

I came across a normal cylinder that imploded fed from a tank. The
draw-off
went through a brass towel rail snaked about a bit and then went up to
the
loft and vented over the tank. When the immersion stat went belly up the
boiling water took the line of least resistance and went up the cold feed
back to the cold tank in the loft. Implosion.

On another occasion: In ye olden day they would put the open vent
through
the roof tiles and onto the roof, not over the tank. The open vent iced
up,
Immersion stat fails and cylinder implosion again.

Oh, I can believe it.

I was easily able to implode my
old copper cylinder with a vacuum
cleaner before putting it on the skip.

The result was rather like one of
those car crushers.
It became very small indeed.
I was amazed.

I have head of, but never actually seen implosions where a few powerful
power shower pumps are taken off the cylinders side. A full body jet shower
was fitted and in the morning when two showers were on, and the dishwasher
kicked in and the kitchen tap was on too the output was higher than what the
22mm pipe from the tank could input. Implosion, not big but a sort of
crinkling of the cylinder. A simple anti-vacuum valve would have prevented
it.

Some thermal stores are fitted with anti-vacuum valves too.