Do the membranes wear out? Could a membrane cause less resistance (back pressure) if it has been in use awhile and the slits have become larger or the rubber less elastic?
A few years ago I had a couple 9" membrane diffusers...off brand from somewhere, and I put full compressor pressure into those discs. Around 10 psi. After a year, the membranes had stretched out to the point that when the air was turned off, they were "loose" on the discs, stretched out big time.
I replaced those, but held onto them as I wanted to take em' apart. I never did, and I rediscovered those diffusers while cleaning out a shed this spring. The membrane had "shrunk"? back to normal size after 3 years, and was taut once again. I can't imagine they would hold their shape if I tried to put air to them again, but at a lower, more acceptable psi, who knows.
