Just to test things a bit further.
I again connected my single Vertex diffuser (the one not currently in the water) direct to my 5/8" line from my compressor and got about 8 psi. The one in the water consistently give me 10psi in 9' of water and sets my relief valve off.
I then took my extra stone diffuser which is probably 8 years old and hooked direct to the 5/8" line from the compressor and got a 1psi reading.
Looks like I will be making a call to see if Ted or his wife can give me some ideas. I feel bad bothering Ted knowing he is struggling with his health right now but would like to try to figure this out.
I'll keep everyone informed of my findings.
This makes me question if perhaps he accidentally sent you an incorrect diffuser model. Perhaps one designed for a lower CFM rating. As Bill pointed out, the diffuser membrane has holes sized and numbered to allow a range of air CFM to escape without excessive back pressure. They strive for the smallest holes/slits as possible because smaller bubbles for a given CFM has more surface area of the bubbles so moves more water compared to a diffuser that creates larger bubbles. That is why the membrane diffusers are generally considered better than the air stones. They can have better controlled hole size and create smaller bubbles for a given CFM.
But I am speculating. I'll fire up my pump and see what happens on my Matala diffusers.
If a person is trying to force more air through a diffuser that is not designed to handle that much CFM, it definitely is going to have back pressure and is also going to be very hard on the membrane I would guess.
