Spring return mid-position valve

[North]

Hi,

I am trying to change a couple of radiators valves and I want to know how to shut the water supply. I have a water pressure tank in the loft which has got a Spring return mid-position valve type MSV 322 in the outlet but I am unsure how to shut it down.
Any advice?

 

[Whitespirit66]

You could get the correct rubber bungs, and bung the outlet hole in bottom of feed and expansion tank, and bung the vent pipe over the tank. This will induce a vacuum allowing you to replace the valves one at a time.

If you are replacing lots of valves, it may be best to drain down. Turn off the water supply to the F and E tank, or tie the ball valve up. Latch your mid pos valve into manual position. Drain the system through the drain cock(s) which will be at the lowest point of the system.

 

[North]

Is there any way to shut the water supply using the valve?

 

[MANDATE]

No you can't close a mid position valve. It's either one port open and one closed or both half open.
If you drain down always latch the valve in mid position when re-filling. (other wise air locks).