Toilet Cistern Ball Valve Washer Replacement Problem - Water Hammer Noises

[Terryphi]

When my toilet cistern fills it produces a loud water-hammer noise. I want to try replacing the washer in the ball valve which is a plastic bottom entry model. I know that the best solution would probably be to fit a new ball valve but I would prefer to first try taking the simpler route of changing the washer in the ball valve. The only snag is that the large plastic nut on the ball valve is very tight and I have been unable to free it by hand. Apart from the difficult access I do not have an adjustable wrench which opens wide enough. Does anyone have any advice on ways of freeing the seized plastic nut?

[proptech]

Hi Terryphi

If this is the common type of valve that has a diaphragm rather than a washer, that nut can be tight. The problem is far worse with lack of space, as what tends to happen is that gripping the nut actually squeezes it on the threads.
It should come undone with hand force only, but if all fails then I'd suggest you get yourself a nice pair of water pump pliers.

[Terryphi]

Hi Proptech,

Thanks for your reply. Yes, it is the common type of valve. I'll get hold of a pair of water pump pliers and give it a go after Christmas.

[Terryphi]

Following proptech's advice I was able to carefully loosen the nut with a cheap pair of water pump pliers. Replacing the washer has solved the water hammer problem.