The float valve on one of my cisterns doesn't seal properly i.e. there is a small but persistent overflow. So - no problem - I will repair or replace it - but not so! The valve in question is 40 years old. I cannot find any suitable replacement. The brass ones available are labelled 1/2" and 3/4". The former is smaller than the old one. It could be screwed on but comes with far too short an arm. The 3/4" is just too big all round altho' its arm is OK. My old valve has a piston which is 7/8" in diameter - so what diameter is used to specify these things?
The old one leaks [presumably] because the circular seal/pad in the end of the piston is worn and possibly the plastic nozzle on which it seats is worn also. Is it likely I could find replacements for these 2 bits?
All your usual v. helpful replies will be much appreciated. Frank