Three way valve replacement

[Scott M]

Need to replace a ACL Lifestyle 3-port valve[1] on a fully pumped, unpressurised system and was wondering if it's possible to do it without draining down as one would swap radiator valves, ie bung up the tank outlet & overflow and let physics keep the water in the pipework.

I can shut off the valve inlet at the pump so there'd only be two open pipes to deal with.

And, FWIW, the valve is slightly below the tank's coil top connection.

Do I stand an earthly or should I just drain?

[1] On dismantling to check it really was the synchron motor, the plastic innards promptly disintegrated so can't just swap motor. And they stopped making it when Drayton bought out ACL so can't just get a new head. Grrrr.

[Roger Mills]

You should be able to do it ok. Bung up the fill and vent pipes and turn off the pump isolating valve. Put old towels anywhere where water may drip. Then break the connection between pump and valve, and be prepared to collect some water (shouldn't be too much) from the bottom of the valve. Make sure that the valve is in the mid position so that you will get everything that wants to come from both sides.

When it stops running, undo the other connections and remove the valve.

[Scott M]

Can beat towels - Wet & Dry Vac. Brilliant for removing water from pipes, rads, etc.

Having thought a bit more, there's not going to be much to deal with as the valve is, bar the header tank, nearly the highest point of the system. So a few pipefulls of water and we'll be home free!

[Fredxx]

I'd also turn all the radiators off as well, just to reduce any movement of water.

I would have thought even if the OP did need to drain the system, with the height of the valve and rads turned off, he wouldn't need to drain off much water.