"David Hansen" wrote in message
...
On Thu, 18 Oct 2007 20:20:24 -0700 someone who may be
wrote this:-

I've just moved my cold water storage tank to the next
floor up, to give enough head for a shower to work. In
scrabbling around in the airing cupboard I found half
a label on the hot water cylinder saying "Grade 4 -
???? maximum 6 metres". Doing some background
checks confirms this means "maximum head of 6 metres".

Grr. With the cold water tank now moved, the hot
water cylinder has a head of 8 meters.

Presumably the cylinder is connected up and has not failed yet.

You might get away with it, at least for a time. You will note from
http://www.plumbingpages.com/feature...Wnewarkstd.cfm that such
a cylinder is pressure tested to 1 bar, which is more than an 8m
head.

It may survive in this situation for months or years or decades, who
knows? However, if it does fail a lot of hot water may well pour
over someone.

I wouldn't leave it as it is.

As he now has the expense of installing new cylinder he may want to consider
a heat bank (thermal store) cylinder and have mains pressure water
throughout the house. No pumps and great showers.