Nate, you have gotten some really good advice. Read it over carefully and all the information is there. I am just going to reiterate a couple things, just in case you did not catch it reading the previous posts.
Your compressor, if in good shape, should output XX amount CFM at a given depth. The deeper the water, the more the back pressure on the compressor, the lower the CFM. As was pointed out, about 6 psi is what your pressure should be at the compressor head to be able to push the air out against the static water pressure at thhe 12' depth plus what resistance is in the line and diffuser. So if the pressure reading is significantly higher than that, something is amiss.
My first suspect is the diffusers might be under sized for the CFM you have, since they were the variable you changed that changed the pressure reading.
A membrane diffuser is sized and has holes to operate correctly at a given CFM flow (actually has a "range" of acceptable operating CFM flows). If there is more air flow (to high CFM) than the holes and size of the diffuser can handle, it will balloon up and force the holes bigger, reducing the output of the compressor at the higher psi while at the same time over flexing the membrane. This will cause the membrane to fail prematurely, like a balloon being over inflated.
IF this is the case (and it might not be, just check the specs on the diffusers for their CFM rating). The output of your compressor at the depth it is running (12') should fall within the range of the sum of all the diffusers added up can handle. If you have more CFM than what the diffusers are rated for, you can either add more diffusers (like a dual, triple or quad diffuser), use a bigger diffuser, or bleed off some air from your compressor so not all the air goes to the diffusers. I personally would want to use all the air you are paying electricity for to compress, even if it meant going to bigger holes and bigger bubbles or a larger or multiple diffuser. But that is just me (and I am not at all an expert).
All of this information was included in the previous posts if you read through them carefully. I have said nothing new, just presented it in maybe a more explanatory way.
Last edited by snrub; 04/27/14 09:26 PM.
