rad valve on steel piped rad in pub. Help needed

[kay-jay]

hi ↲Hope someone can give some advice. I've been asked to look at a badly leaking rad valve on am old steel rad piped up in steel. Landlord says he has a replacement valve. My questions are. . . Because its a big pub and a big heating system what is the best way to isolate the water? Should i close all rad's and drain all the pipe work and refill and balance after the valve swap? Any advice really appreciated.

 

[helpsy]

Freeze the pipe.

 

[kay-jay]

nice one helpsy.

in the end it was only a nut loosened by some plonker at the pub with an axe to grind.