"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.