"Jim GM4DHJ ..." wrote in message
...
On 05/08/2018 12:47, Jim GM4DHJ ... wrote:
what is the nut for on a non return valve in a CH pressure loop ?...is it
for draining ? ... or what?


as seen here

https://www.youtube.com/watch?v=SkxVu8LFCz8


well I don't know either......