I need to replace a 22mm valve between the water cylinder and boiler. Do I have to drain the chylinder?
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Turn off the cold water supply to the cylinder which is most probably coming from a water tank in the loft. Next open all hot taps to drain hot water to top of cylinder. If you can find drain off tap on cylinder, then attach hose pipe and drain it out. unscrew the valve unions slowly to check that no water is leaking out.Remove old valve and replace with new one. refill cylinder after closing the hot taps and closing the drain off. when cylinder stops filling, open hot taps to get air out of the pipework, then continue filling cylinder. Check valve joints are not leaking.
well how else will you isolate it? if its just a gate valve, then you could possibly freeze the pipe, and change the valve... but at 7/8ths thats a big old bore...
drain and refill... safer and possibly quicker...
You'd only have to drain anything which is higher than the valve.
Dont forget to turn the main water supply off!!
Depends on whether it is a cold feed, a hot water draw off or a connection to the boiler hot water system heating. If it is the latter you will need to drain down the heating circulating system as this indirectly heats the water cylinder.
A lot has to do with how the valve is attached,threads, sweat or a combination there of .If a sweat connection is required definetly drain the cylinder(I guess you mean the storage tank.) Of course shut off the cold water supply. I would guess you have no experience in this field I suggest that you get some one to help with plumbing expertise. Through years of work in maintainece I've found the simplest job could turn out to be a nightmare. Get help I really dont understand what the valve is for.
If its from the boiler and the boiler is also supplying the central heating system you will have to drain the heating system if there is no other form of isolation.
Providing the cylinder is of the 'indirect type' i.e. the tap water does not use the same water as the heating system then you will not have to drain the cylinder.
If the cylinder is of the 'direct' type then draining the central heating system will drain the cylinder as well.
Don't forget to add a good quality inhibitor to the heating system when refilling.
I'd call a plumber if I were you.
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