How Much Is Reverse Osmosis Tank Pressure When Full?

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While an empty RO tank should have a psi of between 6 and 8, when it is full, shouldn’t it be higher?

Yes, it should. How much higher, exactly?

Read on to find out.

Key Takeaways

  • The psi of a reverse osmosis storage tank when full depends entirely on the pressure of your feed water. In general, the psi of the storage tank, when full, should be two-thirds of the pressure of the feed water.
  • At 40 psi feed water pressure, full tank pressure will approximate 26.7 psi.
  • At 60 psi feed water pressure, a full tank will read around 40 psi.

How Much Is Reverse Osmosis Tank Pressure When Full?

As a general rule, the pressure in a full reverse osmosis storage tank should be two-thirds of the feed water or incoming water pressure. This means that the higher the pressure of your incoming water, the higher the pressure of your RO storage tank.

We have done some of the calculations for you!

  • Feed water pressure is 40 psi, then full tank pressure = 40 psi *2/3 = 26.7 psi
  • Feed water pressure is 50 psi, then full tank pressure = 50 psi *2/3 = 33.3 psi
  • Feed water pressure is 60 psi, then full tank pressure = 60 psi *2/3 = 40 psi
  • Feed water pressure is 70 psi, then full tank pressure = 70 psi *2/3 = 46.6 psi

Under Sink Reverse Osmosis System

How to Pressurize an RO Tank Properly

If your empty tank isn’t sitting between 6-8 psi, you will need to pressurize it. If it is sitting above 8 psi, then you will need to depressurize it! Here are the steps for both.

  1. Shut off the water to the RO system.
  2. Also close the RO tank valve.
  3. Disconnect the tank.
  4. Take it outside or to any drain.
  5. Flush out as much water as possible by opening the tank valve.
  6. Drain the remaining water by increases tank pressure using a bicycle pump or a compressor.

Now that the tank is empty, use a pressure gauge to measure the tank’s psi. If it is lower than 6-8 psi, you must repressurize it using your pump or compressor. Do this slowly and carefully.

To depressurize your tank, simply push the stem in the center of the Schrader valve.

Now you can reconnect the tank and continue normal operation.

Why Do RO Tanks Lose Pressure?

The main reason that RO tanks lose their pressure over time is simply due to air seeping from the tank. You will notice the flow rate of your water decreasing when this happens. This means it is time to drain and repressurize your empty tank.

If the problem persists again a couple of days after pressurization, there may be another issue, such as a ruptured bladder tank.

What’s a Reverse Osmosis Tank and How Does It Work?

An RO storage tank is known as a hydropneumatic pressure tank. This means it stores both air and water inside it, with the air and water sections separated by a rubber bladder. The air is pressurized, ready to send water through the faucet the minute it is opened.

The water that the reverse osmosis storage tank holds is completely filtered. Systems come with a storage tank because reverse osmosis is a slow process (one drop at a time level slow), and it is helpful to have a ready supply of water on hand for immediate access.

The tank itself is usually made of steel lined with butyl.

If you have any questions about RO tank pressure when full please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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