A bit more information for you all.
I made the problem initially for myself I guess by combining the return flow from the Underfloor Heating (UFH) & the return from the normal radiators at a point where the rads return comes down from the first floor.
Everything is pumped. The UFH is...
A hissing noise as the water is pumped passed the spring diaphram. This is amplified in a nearby bedroom radiator.
I guess you can't mount a swing check valve to stop upwards gravity unless you create a dog leg in the piping so the valve in the right way up. Maybe the pump is not powerful enough?
Noisy Check Valve.
I've just installed a check valve (sprung loaded) and it stops the unwanted gravity feed to a bedroom radiator but it is noisy.
Will it settled down? The system has just been refilled and there maybe some air to be bled out and I haven't put the inhibitor in yet in...
The underfloor heating return gravity feeds the wrong way up to the bedroom radiator via the bedroom return pipe. What kind of valve will stop this reverse flow please?