i have just replaced the valve in my toilet cistern - the water supply is an old metal pipe, the shank from the valve is plastic.
The tip of the metal inlet fits into the plastic shank and the threads line up and the metal tap connector fits the thread of the plastic - it still leaks!!
what is the best way to seal the join?
The metal tap fitting should have a fibre washer in it. Make sure that this is present and it good nick.
If this is not the problem I would use Plumbers Mate. It will never set hard like silicaone, so can easily be removed later.
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