Hi, This can be done in several ways. One of the way i am discussing
1. You buy an identical pump and swap the bodies (you can't expect to do this with every model), and the valves hold up.
2. You swap the entire pump for an identical one, and the valves hold up.
3. The valves don't hold up, and you end up having to drain the system (or most of it), and you fit new valves.
4. You fit new pump and valves, but the distance is different, and you have to alter the pipework.
5. You do one of the scenarios involving valve replacement, and you stand back in amazement, then, when you refill, nothing happens, because there's a blockage in the cold feed. You cut the cold feed near the tee, and sweat and swear because it's hard to get at, clear the blockage, reconnect, refill, vent, and emerge triumphant with several shiny new synapses inside your head.
6. As per 5, but you forgot to add inhibitor, and months later your rads start to spring pinhole leaks.
7. As per 5, but you remember to add inhibitor, and to clean out the system first, but the system was badly corroded and weeks later your rads start to spring pinhole leaks.
8. You get a heating engineer to do it all.
BTW, when you vent - do it with the boiler and pump switched off (i.e. turn everything off at the programmer).
Oh, and the same applies to working on the pump's electrical supply.
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