Thanks, what I've done is check the part numbers, it's as I thought, the valve body is a common part. That's the good news. The bad news is that the flow to hot water, ie with the valve energised, exits from the opposite side of the tee in relation to the mid posn valve. So it's either a drain...
Thanks Mr Banks, that's not something I had considered. Would you know if the (Drayton) diverter valve and mid point valve share the same brass bodies? If so, this would be great as it would avoid a system drain down.
My system has Wiser valves fitted to all radiators on a Y plan system powered by an oil boiler.
I've been thinking for some time, as per Blue, that as the wiser valves give control over each rad, the mid position valve is basically redundant and could be replaced with a simple zone valve on...