I have suffered from pump over since I replaced a seriously sick pump
about 3 years ago. I have an old vented C/H system with a Potterton
Netaheat boiler. As I could not cure the problem I had decided to live
with it whilst reducing the effects as much as possible, i.e. putting
a cover over the header tank to stop the condensation soaking the
loft.
Anyway I decided to have another look this morning and noticed there
was a short (1 metre)15mm pipe run teed into the flow side of the pump
and teed into the exit side of the immersion tank pipework. There is a
stop valve midway along this pipe which was open and when I closed it
the pump over stopped immeadiately. Can anyone tell me the purpose of
this "bypass" and assure me that I have not done anything I should'nt?
Have I really cured my pump over by closing this valve?. iIt will
certainley make my Xmas if that is the case.

Thanks

D