The dump valve on my Nimbus 3 are leaking - one leaks about 10 litres
overnight, another 10 litres an minute, the others somewhere in between.
I'm looking for help on how to go about sealing them better.

I will get some new springs manufactured to push the valves closed but I
would appreciate help on how to renew / refurbish or repair the existing
seals themselves.

Tkx
Ian