I had not seen that previously. Brian White's post is great because it nails down the circus of why one reader's test rig had low output, rather than allow people to be discouraged. He's doing well. The psi is determined by the height difference between the water output and the surface of the (still) water in the bubble separation chamber. He's closest to that. The reader was using about 1 meter difference.
The pressure I have to work with is considerable because I'm using tapwater. I don't need all that pressure which is in the water supply mains because I'll just use an elevated water tank to supply water to the house and garden after I've used up the excess pressure by making compressed air.
I have a pressure gauge on the household mains water supply, it reads a little over 75psi or just over 500kpa which is equal to 50 meters high. (50 yards high) So it could fill a tank that high, and I could use that for the input and then use a tank for the output at 5 meters high (5 yards high) to supply the used fresh water to the house and yard.
Feet of Water = PSI x 2.31
PSI = Feet of Water x .433
mH2O value = kPa value x 0.101972
1000 kpa = 101.972 meters head
It is not practical to use a tower or tunnel 50 meters high or deep, so stages must be built,