I have a gate valve located in the airing cupboard that turns the hot water on and off. It has seized up over time and may need replacing. Are there any plumbing tips to try to unseize it or if it needs replacement what is the easiest way to change it. Do I have to turn off the cold water stop cock and drain all the hot water and the cold water tank? There is a hot water cylinder in the same cupboard and the gate valve is on a vertically rising pipe.
I have a gate valve located in the airing cupboard that turns the hot water on and off."
"There is a hot water cylinder in the same cupboard and the gate valve is on a vertically rising pipe"
lead me to want to ask whether the gate valve in question is either fitted to the cold feed down from the CWST in the roof which goes into the BASE of the cylinder or fitted to the hot supply pipe out of the cylinder which comes out of the TOP.
Mostly it will be the former, I think thats what you are saying and I think thats what HE has assumed but some nagging little doubt wants me to ask you the question anyway because there'll be a slightly different solution.
Also please advise if there is a gate valve or stopcock on the ouitlet from your CSWT in the roofspace.
Further to what rosebery said, if the gate valve is on the cold feed to the base of the cylinder and the valve is below the top of the cylinder, then the cylinder will need to be drained down to below the level of the valve after the hot tap has stopped before removing the valve. If the valve is positioned higher than the cylinder or on the hot water outlet from the top of it then the method outlined by htg engineer is fine.
The valve is positioned higher than the cylinder, however I will check whether it leads to the base of the cylinder or whether it comes from the top of the cylinder. I will pay a visit to the CSWT to see if there is a stop cock fitted in the roofspace. If there is, is it better to disable the cold water supply from here rather than the main cold water stopcock?