I don't do most Dendros or large, "floofy orchids". For me it's minis (like Angraecoides), Masdies, Paphs, and others that crept in somewhere along the line. See my orchid list for complete collection (usually not current.)
On google I've located one or two formulas 1 PSI = 2.034 feet of lift (or aproximately) but it seems dependent upon the volume of water your moving and diameter of the tube. So I'm going to try my experiment anyway since I bought an extra water pump...
1 psi = 2.3 ft of friction-free lift. If 'lift' is through a pipe, you will get less lift per psi. Other sources of friction loss, misting heads, etc., have the same effect.