"MrCheerful" wrote in message news:GnV4c.16150
Good, thats that sorted. Out of interest, 3 - 4 years is about average for
hard water.
I have a water softener, in twenty five years I have replaced the element
once, and that was the one which was here before the softener. The water
heater is on semi-permanently too!

May seem like a silly question, but is 3-4 years normal even when the
immersion heater is not used?, (ours is a backup for the gas boiler
which heats the tank by indirect coil).