Pics of my pump and the valves follow (pump is upside down) ...
I'm not sure if my system has a drain off but I'm guessing that one of the two highlighted areas is the drain cock?
The screw on the valves turn ok but they look like the 2nd of the two valves you put up (the type you've just warned me about Corgiman). The pipes are 22mm.
Whilst writing - can anyone tell me what model pump this is (can't see any markings on it). I've searched on the internet for MySon pumps and the closest match by looking at it is the CP53 but this looks a (very) old version!
The view from underneath (poor focus) is ...
Thanks for your help once again guys - it is really appreciated.
Those valves look really old and ropey, and I bet at least one of them will be jammed. Clean up the old pipework with wire wool before fitting new. The old pump is probably the same width as your new one, but try for fit before making the joints.
The drain off you show is higher than the pump, so there will still be water below the drain. See if you can find any other drains.
If one of your rads is on a hard floor that won't be harmed by water spillage, it is possible to drain by loosening a rad valve and holding a bowl underneath. Rather a slow job, though. It is also sometimes possible to screw the connector from a garden hose or a washing machine filler hose onto a radiator valve, which makes it easier to drain out of the hose into a sink or bucket.
A very handy thing to have is a radiator valve with drain-off incorporated, I have these on all my ground floor rads (but the best time to fit them is after you've drained down). So you might think about these to save you trouble next time round.
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