Reverse Osmosis storage tank air pressure.
You can tell when the storage tank needs some more air when the volume of water delivered quickly is not very much and when you have run it out the storage tank is still heavy then the storage tank air charge needs topping up.
Reverse osmosis storage tanks have an air charge section and this needs to be topped up about every 2 to 4 years.
Turn your reverse osmosis system mains water in-feed water supply off, turn the ball valve on the top of the storage tank off and disconnect the tubing that supplies water to and from the storage tank.
Take the tank outside and open the tank ball valve to release any water pressure that is there. With the water valve in the open position start to put compressed (pump) air into the air valve, some water may come out as this is done, if so continue putting in the air gently until no further water is expelled from the tank ball valve.
Pressurising the storage tank can also be done without disconnecting the tank. Turn the in-feed mains supply off, open the faucet and the storage tank ball valve and run all water pressure out via the faucet. Start putting in the air via the air valve and pressurise as per below.
Special note, the air valve on these storage tanks is set lower into the valve than a car tyre valve so be sure you have pushed the pump valve connector on far enough.
The ideal pressure for a completely empty storage tank is 6 to 7 psi (45kpa) air pressure but because most air pressure gauges don't go down that low pressurise past the 10psi mark and then bleed off excess pressure back to 10psi or slightly less and leave it at that.
Re-connect the storage tank to the system, turn the mains in-feed supply back on and allow about 1 hour for the tank to re-fill. If the air charge is quickly lost again then either the tank has failed or the air valve is faulty and needs replacing. If water comes out the air valve the tank has failed internally and needs replacing.
Due to the large volume of air a bicycle air pump will tank a long time to pump up the air so a compressor or car type pump is more suitable.