Hi All
Daughter has an unvented hot water cylinder in her flat which has two
3kW heaters. We believe (although I haven't checked as shouldn't really
travel) that the bottom (main) heater has failed and needs replacing.
Apart from getting the correct length and thread diameter of the new
heater, switching off the electric to the timer, and draining the tank -
is there anything else I should look out for when doing the replacement?
I have an immersion heater spanner already.

It's an Albion (now part of Kingspan?) cylinder, 170l Stainless
unvented, SU170D. I can't track down the heater part number which is
14P395 "STAINLES" (sic) but it seems to be a normal 3kW part. I assume
the thread is 1 3/4 but I don't know what the length should be 11" or 14".

TIA for any help.