valves

nadiahealy

Could anyone tell me why there are two types of non return valves, a spring type and a flap type? Does it matter which one you use?

youtheman

The main difference is that the spring type needs a fair bit of pressure to over-come the spring force. The spring-type is more of a 'tight shut off' as the spring helps press the valve up against the seat. The flap type is more to stop 'gross flow' in the reverse direction.

You also have to be careful how you orientate the flap type in a pipe, if the pipe is vertical then you could have gravity keeping the flap held open.

I had to fit an NRV on the pipe from my central heating header tank. As the presuure was very low I had to fit the flap type, and make sure it was on a horizontal line. The spring type would not have worked as it would always have been stuck shut.

So if you want 'tight shut off' is a high/medium pressure line use the spring type. If you want to prevent gross reverse flow in a low pressure line use the flap type (but make sure you install it correctly as regards orientation).

Hope this helps.

nadiahealy

cheers that leaves the understanding of it a bit clearer,thanks for reply.

kay 9

Flapper type on solid fuel.

nenil

I've just has 2 'spring type' NRVs fitted to my heating system that has Oil heating pack and a Rayburn.
At the time of fitting I was worried if the Rayburn pump or electricity failed the spring NRV would prevent the gravity heat circulation from the Rayburn....

Should I worry?