Reverse osmosis - tank pressure?

Hi all. what is the best pressure to charge a RO holding tank too?

Typically 6-8 psi

psi

The lower it is the more water it will hold. The system itself will establish the operating pressure.

And the lower it is the faster the draw down gals are used up and the membrane starts making water, and flow goes to next to nothing; dribbles actually.

The air pressure should be set at what the manufacturer suggests; which is usually 7-10 psi with no water in the tank.

pressure

Not really. The air charge will be at system design pressure when the membrane shuts off. The water will then discharge at exactly the same rate regardless of the initial charge. BUT when the water usage drains the tank down to the manufacturer's recommendation the tank will be empty and water will cease flowing. If the charge was actually less than that the water will continue to flow at a slower rate until the tank is empty.

Yes really.

The water flow reduces as the tank empties because the pressure reduces to 0 psi, the same as a well pump pressure tank does.

When the tank empties the output of the membrane trickles out the faucet instead of going into the tank. It only goes into the tank when the faucet is shut off.

Tank Pressure problem?

Yeah I had a similar issue. What Gary said may be simple but it was my first installation so I was not thinking straight. I didnt have very good water pressure, i finally figured out that the tank needed back pressure to work (the faucet in the off position) Duh

IF the pressure is TOO above the system pressure, the RO unit cannot push any water into the tank, so you get ZERO volume from it and the only flow is from the membrane. If the pressure is ZERO, the tank will be full of water but there is no air to push it out, so you only get the water flowing from the membrane. Under ANY other situation the system will compress the air to its working pressure and it will deliver water until the air pushes all the water out of the tank, at which time the flow will diminish. The higher the pressure the LESS water the tank will hold, and vice versa, but it will be at the precharged pressure at the time it stops flowing.