I think each Vertex diffuser should take all the air direct from the compressor with 0 back pressure. Ask Ted to connect one of his single diffusers to a 4cfm pump and see what his psi reading is. IMO pressure should be 0 not 10psi. Something seems wrong with this picture IMO. A normal Vertex diffuser should not cause that much back pressure. The only way the psi should be 10 for one diffuser is the holes/slits are smaller than 1 millimeter and too few of them on the membrane.
Snrub thanks a lot for the link to the Thomas compressors. Very helpful.
Bill, I may be all wet here because I am speaking from what my "minds eye" sees and not from practical experience, but I would expect more back pressure from the diffuser at shallow or no depth than from deeper depths. For example, at 10 feet depth, the compressor already has to overcome the static water pressure at that depth. The diffuser might only add an additional tenth psi or something very small to open the slits for the bubble to escape. But I can see where there is no back pressure from water depth, it is going to take something to balloon up the diffuser and cause the air to escape.
I could be all wrong about this. I have no engineering data or practical experience to back it up, just what would seem logical to me. Would be nice if one of the aeration sales experts could come on and give some examples or explanations as I am interested too.
I do know if you connect a dual Matala diffuser to a pump at about 4 cfm it will balloon up when done so on the surface. Did not have a pressure gage installed at the time (have one now). I have not watched it at depth (will this summer when I scuba dive the pond - will try to remember to take pictures) but I would expect the membrane to move very little. Seems I read somewhere it is not particularly good to balloon up the membranes as it is hard on them.
I'm going to run a linear diaphragm pump which looses cfm rapidly at depth, but they are very economical on electricity at shallow depths. My CFM drops in half from surface to 10' and max depth for the pump is only about 12' (where the output would approach zero beyond that).
I've got mine setting out in the shed. If I think about it tomorrow will hook it up and see what happens to the pressure on the surface with the pump turned on.
Again, this is just speculation at this point on my part.
