HOT WATER tap+Washer HELP

[PACH1]

I need to replace the washer of the hot water tap in the downstairs WC. The hot water comes from a cylinder in the airing cupboard upstairs . Any ideas how do I turn off the hot water? There are a few taps in the airing cupboard where the cylinder is. I thought I turned off the cold water feed to the immersion tank and let the hot water out but when the hot water ran out, cold water started comming out of the hot water tap. At this stage I gave up.
Any ideas please?

 

[wonderb0y]

If their isn't a gate valve to stop the water coming out of the tank, then turn off the mains, or tie up the ball valve in the loft, and run a few hot taps in the house to drain down the tank, either that or bung the feed pipe in the tank, empty the pipes and change the washer.

 

[PACH1]

thanks for your help. in the mean time I found the cold water feed into the cylinder and turned it off; run the hot water taps for a short time and changed the washer.