What is the name for the valve that prevents gravity circulation into the heating system on an old system that uses gravity DHW Circulation and pumped C/H. Searched for Anti Gravity without success.
Looking for something as an interim measure to prevent upstairs radiators getting warm when pump isn't running. Next year - new system
On Tue, 14 Aug 2007 21:19:26 GMT, "John" mused:
Anti-gravity or check valve?
A spring check non return valve would probably stop it. Having tried that, I'd suggest a 2-port zone valve. Thermostat & timer in series operate actuator, the end limit switch closes and starts pump. Re-use it next year with another one on the new system, instead of a 3-port mid-position valve (unless it is to be a combi).
Check valve - probably a single check valve will do in that application.
Colin Bignell
gravity check valve or swing valve I think - look at
if you use a single check spring check valve as others have suggested take out the spring or it'll make a devil of a noise with the pump trying to push water past it. On some designs it's quite easy to remove the spring: others are next to impossible, so check beforte buying. The type intended for a shower (1/2" BSP female * male) might do (though not really intended for CH temperatures)
Single check and double check valves
You could fit a swing check valve ( Part No 7518, etc). I fitted one to stop gravity flow once. It didn't work, the convection drove the water past it as though it wasn't there. It's usually only a problem with boilers of a high thermal mass.
Spring check valves ( Part No 7521, etc) are often used to stop gravity circulation. I've never heard of the spring causing noise problems. I fitted a zone valve and would do the same again.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "John" saying something like:
Dribble Valve; sometimes known as a John or Adam. Care should be taken when installing as they're likely to get screwed up.
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