Hot water confusion

[Philpow]

Hi I need to replace the valve core of the hot tap in the downstairs toilet the cold tap was a breeze just turned the water off at the service tank the hot tap however is another matter having turned the supply from the tank off in the airing cupboard I endeavoured to drain the pipework by turning on the kitchen hot tap after about 10 mins there was no sign of the water stopping indeed I can hear water going into the loft tank to replace it!!!???
The only thing that comes to mind is that the valve is duff??
I am loath to throwing away a lot of hot water plus the cold water in the tank so any Ideas anyone?

 

[Burnerman]

If the loft tank is still filling then either you have turned the wrong valve or the valve itself is faulty......the copper cylinder fills from the pipe that enters the bottom of the cylinder so you may like to check that.
Tying the ball valve up on the loft tank will minimise water loss and allow you to carry out the work - at least to the capacity of the tank.
John

 

[dilalio]

If there are no shut offs on the HW outlet from the top of the cylinder or on the cold feed to cylinder from the large loft tank, then you will need to bung the low level outlet from the loft tank to the cylinder - find out which one it is then bung it with a carrot - it will mean getting ur arm wet, which isn't as bad at this time of year, compared to the depths of winter!