Just dry fitting some pipework from my plant room to the ufh manifold under the stairs.  The pipework rises from the 3 port on the cylinder and follows a route through the ceiling joists where it finally drops to the manifold.

 

Most design docs call for air valves at the highest point so I will install one at the point above the ceiling after my 3 port valve before the pipe turns to go to the UFH manifold.  I've read that the auto valves sometimes leak when they get filled with crud, or when they get old, so with this in mind I think I'd rather install a manual one.  I'll also be installing an access hatch too into the ceiling space above the plant room for future access... Unless there is a better way?

 

Pipework to the manifold will be 22mm can anyone recommend a half decent valve and do I need one on the feed and return, or is it just the feed.

You need them on flow and return or an air bubble will just sit there.

 

These seem quite good Inta 15mm Automatic Air Vent AAVB15 I got mine from here

 

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