"BigWallop" wrote in message
...

"john" wrote in message
...
Around my central heating pump there appears to be what looks like a
by-pass
loop (with 15mm pipework) containing a gate valve. What's the purpose of
this loop and what should be the setting of the gate valve (fully open,
fully closed or somewhere in between) ?



It is balance pipe John. It is there to make sure that there is always a
flow of water through the boiler, even if it is somewhat restricted, when
all the motorised valves are opening and closing and the pump stops and
starts, and it just makes sure that there is that flow to stop the water
pressure, mind it's heated and expanded, from hammering the system to
bits.
Start it at about half way, turn it all the way in till it stops. Now
turn
it all the way out but count how many times one of the head stocks passes
a
certain point. Now turn it in half that amount. So if it did 6 full
rotations, then turn it back in 3 full rotations.

If you hear the system giving a thump when the demand for heating or hot
water is asked for, then give it one turn out. If it seems as though it
is
taking to long to heat the water, then turn it one in, and so on.

Hope this helps.



Yes, your explanation has been extremely useful. Many thanks.