Anti gravity valve

[brennan50]

I have a back boiler system with pumped central heating and gravity hot water. Radiators are heating up on hot water only. I have replaced anti gravity valve with single check valve but still same problem. Any suggestions from the experts??
What is a double check valve?? can that be used ?

 

[cider]

some of the rads may be tee'd into the cylinder flow as an old heat leak circuit if the systmem used to be solid fuel.
Dont fit a double check valve, its not designed for that use

 

[namsag]

Have you fitted it the correct way up or dirt in system stopping it reseating properly.
Sprung ones are the best