"Brian Gaff" wrote in message
...
Luckily our tank is designed a bit more sensibly than the one in your
example and it can be all drained down and isolated enough to get the
element out without a completely empty cylinder. I am eternally amazed
though when you get the heater out how bent and encrusted it gets just
heating water. Brian

My hot water cylinder had the header tank joined onto the top of it (*), so
there was no explicit inlet feed pipe to disconnect. The outlet needed to be
unscrewed (after I'd emptied the header tank and hot water system as much as
possible by opening the hot taps) and then the tank was "free" to be rotated
on the baulks of wood that it was standing on. That makes it sound very
easy: in practice it was a case of tipping it onto one baulk, rotating it a
bit, rocking it onto the other and rotating it etc, which took a while to
get it far enough round to reach the drain cock. Which silly herbert
designed the tank with the drain cock on the *back*?

Cylinders with the element going in vertically through the top don't need to
be drained, but I could see that mine would need to, because it had two
elements (daytime and Economy 7 tariffs) going in through the side: the
daytime one heated the top 1/3 of the cylinder and the night time one heated
the whole cylinder.

When I got the element out, only half of it was the the ends of some of
the loops were still inside, having exploded off when the thing shorted out
at 1AM when the Economy 7 timer turned on - made a hell of a bang and left
black scorch marks on the fuse box.

I removed the cylinder completely (carrying it downstairs on my own was
amusing!) and hosed it out on the drive, and there was a *lot* of limescale
in the bottom - plus the remains of the element. I'd estimate several
kilogrammes of limescale, which probably filled up to the level of the lower
heating element. And that was with only about 5 years' use, because the
house was only 5 years old from new. While I had the tank out, I removed the
other, daytime element and checked that, but the metal was still shiny
because I imagine it had not been used nearly as much except for
occasionally topping up the hot water if all the water heated overnight had
been used up.


(*) Saves the builder the hassle of putting a header tank, a cold water feed
and a pipe from tank to cylinder in the loft. It was a bit noisier because
you could hear it gurgling in the airing cupboard as it refilled after
running hot water, but it worked well enough.