"Rob" wrote in message
oups.com...
Hi,

This morning I noticed a fairly significant bulge on the top surface of
my hot water cylinder (standard gravity fed system, gas heated with a
backup immersion that we never use). The insulating material is cracked
around the immersion heater and the pipe that goes in at the top (which
I guess feeds the coil from the boiler?). There's no sign of any leak,
although some silicone-like substance has oozed out around the
immersion heater.

It's obvious that I probably need a new cylinder but I have some
questions:

- What might've caused it? I thought the system was vented, so no high
pressure was involved?
- Is it safe to carry on heating the water or should I leave it
switched off? I guess the latter, but my wife is nonplussed about that
idea.
- How much is a new cylinder likely to cost?

Thanks in advance,


I would drain the system down, to relieve any stress and impending disaster,
and remove the insulation from around these areas. Hopefully it'll just the
insulation which has swelled up due to this leak.