I am building a home aquaculture system using air lift pumps. I have formulas for calculating water flow and for metering my cfm with orfices. My question is how does water depth effect air flow. I know that 1 psi = 27.68 inches of water. So my question is do I need to increase my psi proportional to inches of water, or will my flow be unaffected as long as my psi is greater than the submergence. Example 1/4" orfice @ 5 psi = 4.43 cfm 5 psi = 138.4" wc. If I submerge the air line 27.68" would I simply increase to 6psi to get 4.43 cfm? Or would my flow be unaffected as long as it was submerged less than 138.4"? Or do I need another equation? Any help would be greatly appreciated.