On Thu, 20 Aug 2009 16:50:22 +0100, Bob Minchin
wrote:

Turning on a hot tap will not drain the tank. Turn on or opening the
drain cock will.

That's what I thought. Our posts must have crossed. I presume the
drain cock is on the cold fill pipe? I'm not sure that mine has one.
Even if it does, the pipe goes behind the cylinder, so I can't get to
it without demolishing a wall ;(

There is no need to remove the element to change the thermostat.

I know. It was just the whole episode got me into thinking about
immersion heaters so after my initial questions about thermostats, I
started musing about everything else!

If you are not using the top heater then why not swap the stats over for
now and get a replacement at your leisure.

Good idea but I've already ordered two.

Maybe even buy 2 to get the protection of the new type on
both your heaters?

Great minds think a like and all that. I don't use the boost function
there's always plenty of hot water left at the end of each day from
the overnight warm, but even so, I thought for the cost of a couple of
pounds, I would replace both so that both have the new safety cut out.

Thanks again.
Stephen.