On 07/10/2020 21:14:23, bert wrote:
Is there by any chance a simple rule of thumb for calculating the
required size of a replacement o ring? I l looked up a supplier and they
had a chart which seemed horribly complicated.

There may well be charts but I have gone by diameter and thickness as
being the two defining measurements.
https://en.wikipedia.org/wiki/O-ring

https://www.theoringstore.com/store/...d=41&chapter=6