Replacing ball valve of tank in loft

5 Aug 2007
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United Kingdom
I need to change the ball valve of the tank in the loft. There is a stopcock on the pipe leading to the tank. The reason I need to change the ball valve is that even after bending the arm to the float the valve is still leaking and causing the water to go down the overflow at most inopportune times (ie at 3.00am and waking me up!). I have a couple of questions....
How do I know what size I need to buy 1/2 inch or 3/4 inch - the tank feeds the hot taps?
Having looked on the internet for purchasing a ball valve there was a site which talked about valves for low or high pressure, how do I know which I need?
How do I go about replacing the ball valve?
Advise would be much appreciated! :)
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Please don't buy one on the Internet - there's very little saving to be had, and it will cost you an arm and a leg in hassle if it arrives faulty or damaged.

Just walk in to your local plumbers' merchant and ask for exactly what Dan specified. Get a new float as well and screw on the float before installing the valve.

If you already have a compatible float valve, then just undo the joint on the part that's inside the cistern, and leave in place the part connected to the cistern. This way you can leave undisturbed that joint that's more likely to leak, and more of a problem if it does.

You'll probably drop the fibre washer into the cistern, but at least I've warned you about it. :D
Many thanks for your advise, I'll certainly follow it and buy a 1/2 inch high pressure valve from a local plumbers merchant.

Now to be really cheeky.....
As i have no DIY skills and would like to learn, is it a difficult job to replace or is it best to get a plumber in? if it's not a too difficult job, can anyone please give a few instructions that might help.

Thanks again
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Wear a head torch, makes job easier. Its a really simple job to do without much knowledge!
Top Tips. You should not be left with "spare parts" once completed :confused:
Dan_Robinson said:
Your mantra with the spanners should be

"equal and opposite force".
You're a man after me own 'eart. :)
Replaced a basin tap valve body last week (amongst many), but only after the owner had "had a go himself". He'd mangled everything, loosened the backnut, and made the tap connector leak.

He went into the kitchen and turned on the kettle, during which time I'd turned off the ball-o-fix and remove the valve body. Stunned, he asked me how the **** I'd done that.

"The right amount of force in the right direction", I said smugly. :D

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