On Mon, 17 Dec 2012 20:11:33 +0000, T i m wrote:

As an aside, I've been able to turn the isolation valves (good old
Leatherman PST II) and I've located a drain cock if it comes to it.

If the isolators do turn, ...

Make your mind up...

... might they not still isolate and if so is it general practice to
change them at the same time?

Are they gate valves or ball valves? I'd almost put money on gate valves
either not turning and/or not shutting off enough.

I also expect that the orginal insaller used fibre washers between the
pump body an valves as well. These will probably have leaked just enough
to cause the pump body to corrode and weld everything together. I've had
to cut pipes above and below and remove the whole lump before now and
even with the lump held in a vice and good grip not being able to shift
the flange nuts at all.

When refitting use ball valves (assuming that the ones there don't work),
synthetic washers and a smear of silicone grease on the mating faces and
thread. This will ensure that you never have to replace the pump again.
Use gate valves and fibre washers and it'll fail within 2 years and the
gate valves will have siezed/not seal, again...

--
Cheers
Dave.