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.

--
Scott

Where are we going and why am I in this handbasket?