"Roger Mills" wrote in message
...
On 28/10/2010 18:05, Scott M wrote:

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?


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.

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.