Reverse Osmosis Tank Pressure and How To Repressurize

If your reverse osmosis system has a water tank in it that’s meant for storing RO water, then you’ll need to periodically check the pressure in the tank and re-pressurize it as necessary.

The proper pressure is important to maintain as that will directly influence how well your RO system works and performs, and how fast water can flow from it.

One way to diagnose whether your tank pressure is off or not is when you realize that the water flow from the tank has seriously slowed down, almost to a trickle.

To see if your tank is defective or if it’s just a matter of pressure, try to relieve some of the pressure from the air valve.

If you see water coming out, then it means your bladder has a hole in it and you need to replace the tank.

However, if there is no water and only air, then it probably means your tank’s air pressure is low and you just have to re-pressurize it.

How to re-pressurize a reverse osmosis tank

Step 1:

Remove the water supply from your RO system and make sure there is no more water entering it.

Step 2:

Turn on the tap and let the water flow out of the tank until it is completely empty. You’ll know it’s empty when the water completely stops flowing. You don’t need to throw the water out – just collect it in a vessel and you can put it to use.

Step 3:

Find the valve stem and remove the covering. Please note that there are two valves – one is the air pressure valve, and the other one goes to the reverse osmosis membrane. Do not remove the valve going to the membrane!

Step 4:

Check your tanks pressure with a PSI gauge. The ideal pressure for an empty tank should be between 6 to 8 PSI for a 2-4 gallon tank.

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Step 5:

If the PSI is below 6, use a bicycle pump or an air compressor to pump air back into the valve until the PSI reaches 6-7.

Be mindful not to over-pressurize.

At this point, you may see that some water comes out of the tank. This is OK. Continue adding air pressure until the water stops again, and then check the PSI.

Step 6:

Once the PSI has normalized, close the valve and the water faucet, and let water flow back into your tank from the membrane.

How reverse osmosis tanks work

RO pressure tanks have two compartments inside them: a water compartment and an air compartment. The air compartment is pressurized and as you open the tap, the air pushes on the water and it flows out through the tap.

Like we mentioned above, an empty RO tank has pressure of 6 to 8 PSI. As water fills up and presses down on the air compartment, the pressure will gradually increase – the increased pressure will then relieve itself as the water flows back out.

Most RO units have an automatic water shutoff that kicks in when the pressure inside the tank reaches 2/3 of the pressure of the water flowing from your main line into the RO system.

If your city water pressure is around 50 PSI, the system will shut off water production when the tank reaches a pressure of 30 or so PSI.

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