The header tank atop my immersion heater has a brass float-operated valve.
It started leaking last year, allowing water to leak out of the overflow
pipe. I took the valve apart and found that the seal is formed by a small
rubber disc, about 8mm diameter. It had become a bit worn on the side that
mates with the moving piston. So I simply reversed the rubber disc so that
the nice, flat pristine side was on the side that touched the moving
piston. All was well, or so I thought.... Now it is leaking again!


Should I now replace the whole valve, or can a new rubber disc be obtained
from somewhere?

These brass valves have been around since time immemorial, and they aren't
exactly cheap. Is there anything available nowadays that is cheaper and
more reliable? Can anyone provide a link to a valve you can recommend?

TIA...

Al