[reassembling post in correct order for quoting]

In article ,
"Geoff Norfolk" writes:
"Pete" wrote in message
...

No hot water tonight is going to be popular. Is there a way forward
without draining the whole system down?

Depends where the valve is and the layout of the rest of the plumbing.
If it's in the hot water circuit (as opposed to the primary heating
circuit) then you just need to empty the loft tank, and if it's below
the top of the hot water cylinder, that too down to below the level.
You might even avoid emptying the loft tank if you can reach into it
and block the outlet with a bottle stopper or something similar.

My guess is the travelling gate has run off the end of the thread for
some reason. You might be able to do a temporary repair by unscrewing
the body of the gate valve, taking the gate out, and pushing it back
into the top as you start opening the valve, until it bites into the
thread again (or you might even risk putting it back together without
the gate in the valve as a temporary measure, although you then lost
your ability to turn off the valve in an emergency). One snag is the
seal between the two parts of the valve body may not seal again when
you reassemble it, and they are a strange size, but it might do until
you can get a replacement.

I've always found those gatevalves a bit unreliable although they are
cheap! I've replaced mine with those ball valves I think they're called
(like the washing machine taps) which seem a lot more reliable. They also
completely shut the water off whereas the gatevalves have a tendency to
dribble a bit.

Use a full-bore one if you do this -- normally with a lever on the top
to turn it.

--
Andrew Gabriel