T
tamz
Check for another NRV on old ch flow on chimney breast, only answer and think you have some how reversed original F & R, ask customer if upstairs rads used to come on with JUST hot water on on BBU, IF THEY DID NOT AN NRV IS FITTED
Not if it was piped by anyone with half a clue how systems worked. This seems to be an English thing. I've fitted and worked on 1000's of gravity jobs and never come across an anti gravity valve yet and neither has anyone i know up here.
To the OP for future reference.
Leave the 1" revolves where they are unless you can be bothered stripping them for scrap.
Catch onto the main runs elsewhere. It is just as easy.