Question:
Anybody know what I should expect to have as a pressure reading at the porton the bottom of the tank? My kid thought it was neat to let all the airout and now I can't get anything out of the tank. How do I fix this?Should I just drain the tank with the schrader core removed ( to put thediaphragm at zero pressure ), then return the core and fill the tank? Ordoes there need to be a certain pressure on the tank when it is empty?

Answer: Air pressure in the pressure tank should be about the lowest pressurethat system ever runs at, or 1 or 2 psi lower. For something like apump or well with a pressure switch, that's easy: If your pump turnson at 40 psi, set the air pressure to 38 psi.

With a reverse osmosis system this is a little harder, since itdoesn't have a terribly well-defined pressure setting. Here's a ruleof thumb I've heard: With the "usual" range of input water pressure tothe RO system (about 40 to 60 psi, which is common for many municipalwater systems, and a tad high but not unusual for well systems), setthe air pressure in the RO output tank to about 7 psi, which meansthat the RO system can usually generate 8 or 9 psi of output ressure.If you have a booster pump in the RO system, you might be able to setyour air pressure in the tank considerably higher, maybe 15 or 20 psi.

Now, naturally, this can depend MASSIVELY on your water systempressure (the input to the RO system), on the quality of your water(the more gunk the RO system has to remove from the water, the moredifferential pressure eat will need), and other such factors.

All in all, I would do this: Take the Schrader valve core out, to makesure everything is nice and at zero pressure. Make sure no watercomes out of the air side of the tank; if it does, the diaphragm ishistory. Then shut off the RO system and depressurize it completely(for example by running the filtered water faucet until nothing comesout). Then pump up the air side of the tank to maybe 7 or 8 psi.Then see whether the system works reasonably well. If it seems tocycle a lot more than it used to, try to change the air pressure.

Or ask a competent installer who knows the water conditions in yourarea.