Chuck, The Vertex Shallow water diffuser wont have a mechanical (blue Brady check valve) unless you installed one, If so remove it. In a Vertex system they are not needed as the checkvalve is intigrated into the disc. That diffuser also has "FlowControl" which equalizes airflow to each discs when installed on uneven bottoms.The orings in the blue checkvalve go bad often and one does not realize this so now its just another restriction that a vane pump does not need to maximize its performance.Stones and Mix Air type diffusers(soaker hose) do need themSome diffusers have them to create back pressure in the line so on startup all of the air does not go to only a few of the diffusers (path of least resistance)Some of these diffusers have wide operating cfm ranges 1-5 cfm and are difficult to balance and flex thus must be removed for cleaning.On a single Vertex CoActive Airstation the range is 1- 2.5 cfm, When you put a Gast 0523 to this single Airststion you are going to get additional back pressure beyond the water depth and tubing size. I just aired up a new 0523 and put all of the air to a new CoActive air station sitting on the shop floor and registered 4 psi with 2 ft .625 ID (ForeverSink Hi-Flo) :)piece of tubing. If you get water in the line the pressure relief valve will do what it is designed to do and protect the system as the water is expelled out of the line via the membrane.
