Plumbing isn't my strong point. Frankly, it's pretty weak.
Yet occasionally it has to be done. We had a leaky cistern, and after plucking up courage we changed a washer.
Didn't fix it. We still had leaks. Clearly more drastic action was called for.
So I ended up changing the entire valve mechanism for a new one. With a quick break in the middle to get some extra tools, and a second attempt to fit it correctly, it was eventually fitted.
And successfully, too. No leaks now!