I want to install a shower mixer tap but I've got a few problems?

[jackpee]

Hi everyone, I've bought a shower mixer tap and would like to install it but I'm not quite sure how I can turn off my hot water supply. I have shut off the main water supply valve which stops water going to the cold tap but hot water still flows from the hot water tap. I don't have a combi boiler, I have a conventional boiler where you have to heat up the water with gas. Do I just have to run the hot water tap until the tank empties or is there any other steps I should take? I also heard that you can create a vacuum when draining the tank and it could rupture it, is this true? If so how do I prevent it?

Any help would be appreciated as I'm no plumber and I'm not clued up on this sort of thing.

 

[ManchesterGas]

It sounds like you don't have balanced supplies, i.e you have mains pressure cold and gravity hot. The shower that you want to use will be no good unless you change your boiler to a combi or your cylinder to an unvented. You can not do either of these yourself.

 

[SimonG]

Close stop tank and open hot and cold until everything stops. Change taps and turn water back on. And as manchestergas says, it wont work efficiently due to the pressure differential.

Oh and watch out for airlocks.

 

[glenno1]

You may need a pressure reducing valve to make the shower effective

 

[jackpee]

The water pressure isn't too high anyways, so would it be necessary to install a pressure reducing valve?

 

[glenno1]

It may not be high but it could still be pushing the hot water back

 

[kris]

Jackpee to save changing boilers and hot water cylinders youl have to run a seperate cold water straight from your storage tank in the loft to shower and either a new hot from the side of existing cylinder (if theres a spare plug in cylinder - drain tank and fit an essex flange this prevents air locks ) if you cant get a new hot supply from a connection on the tank then depending on your system layout you might get away with simply teeing off a hot pipe near the hot water tank. The flange is the best way,

DRAINING,
Remember you only need to drain tank if fitting a flange otherwise all work can be done with the tank / (when i say tank i mean hot water tank) still full,,,
Like the guys said switch water off and wait for taps to run dry , once the hot tap stops running this means the cold water tank in attics empty but the hot water tank is still full, 9/10 times there will be a drain cock at the bottom of the tank that you can attatch a hose to and run it right outside, but if there isnt i usually disconnect the fitting at the top centre of the tank and syphon it with a hose, there will be no vacuum as air escapes past the hose, but if your unsure about draining a system it might be BEST TO CALL IN A PRO , he will be able to do what ive said, and even with poor flow you can fit a shower pump onto the 2 pipes ive described to up your power/pressure, again this would depend on size of tanks and position of pipes and shower etc, hope this helps mate,,