Vertex diffusers have a built-in check valve-air balancing mechanism in their diffuser heads. This causes some additional unavoidable back pressure for the system, thus your 9psi reading for a max of 8ft of water. I think this is one of the reasons why Vertex prefers the higher pressure rocking piston compressors as standard items for their aeration systems. To check the built-in back pressure of your diffusers just hook them up out of the water, close to the pump, using unobstructed airline such as garden hose. Unhook the diffusers and see how much the psi drops (which should then be 0psi open flow from the pump). All you are doing is testing the air flow restriction of the diffusers.
Last edited by Bill Cody; 03/28/19 09:13 AM.
