Reverse Osmosis Tank Pressure – How Much PSI Is Correct?
Written by: Gene Fitzgerald // Last Updated: Mar 14, 2023
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Are you feeling under pressure regarding the smooth running of your RO system?
It can be confusing to remember all the facts and figures when it comes to how to have your RO storage tank running optimally.
So, to take some of that pressure off, here is our handy guide that covers the numbers you should look for when it comes to your RO storage tank and what to do if you feel like it isn’t functioning correctly.
Contents
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Key Takeaways
- When your RO tank is empty, the PSI should sit between 6 and 8.
- When your RO tank is full, the PSI should be ⅔ of your feed water pressure.
Reverse Osmosis Tank Pressure – How Much PSI Is Correct?
When your RO tank is empty, the psi should sit somewhere between 6 and 8. Double-check the label on the tank or the manufacturer’s instructions, though, as it may vary between models.
When the tank is full, the general rule is that the psi is about two-thirds of your feed water psi. So for example, if feed water pressure is about 60 psi, you can expect a full RO tank to read around 40 psi.
Can I Add More Pressure to Increase the Flow Rate from My RO Faucet?
It is best not to do this. More pressure inside the tank means less room for filtered water! It would also mean an increase in wastewater, as backpressure from the tank would cause more water to flow down the drain line.
How to Repressurize an RO Tank with Air
Over time, your RO tank may lose pressure. This means you will need to repressurize it. You can do so by following these steps:
- Shut off the water supply and close the storage tank valve.
- Disconnect the tank and take it someplace you can drain the water.
- Open the valve and let the water flow out until it is down to a trickle, then pump air into the pressure valve to get the remaining water out. Bicycle pumps are great for this.
- When the tank is completely empty, measure the psi to see if you need to depressurize it or pressurize it.
- For pressurizing, pump carefully with a compressor or bike pump until the psi reaches 6-8.
- Reconnect the tank to your reverse osmosis system, open all valves, and let the system refill.
Why Do RO Tanks Lose Pressure?
The main reason RO tanks lose pressure is simply air seeping from the tank over time. A gradual decrease in water output from your RO faucet will reflect this.
What’s a Reverse Osmosis Tank and How Does It Work?
A reverse osmosis storage tank is usually a steel-made tank with a butyl bladder. Its function is to store water that has been filtered by reverse osmosis to ensure you have water ready to drink whenever you need it. Reverse osmosis is a slow process, so the tank keeps water at the ready to flow into your RO faucet when you turn it on.
The tank is what is known as hydropneumatic, which means it stores both air and water. The air is pressurized, so when you turn on your faucet, it propels the water up and through it. This means you do not need to install a noisy booster pump for your RO system.
An RO storage tank also creates backpressure. This switches the filter system off – think automatic shut-off valve – once enough water has flown into the tank and backpressure has reached a certain level. Your RO system will continue operation once water is drawn from the tank by opening the RO faucet.
What to Do If Your Water Storage Tank Isn’t Filling Fast Enough?
If your reverse osmosis storage tank is not filling fast enough, and it is a new system, be patient. They generally do take a long time to fill! Between 2 and 4+ hours is about standard. If you have waited several hours and the tank is still not filling, then it is time to troubleshoot by going through the following list.
1. Shut-Off Feed Water Valve or Storage Tank Valve:
Double-check your feed water valve first to make sure it is open all the way and not shut off, then double-check the valve to the storage tank and make sure that too is on all the way. It seems simple, but it is easy to overlook the valves after installing a new system or maintaining one. Filtered water will not be able to be made if there is no water to filter!
2. Low Feed Water Supply Pressure
In order for your RO system to function optimally with minimal wastewater, your home feed water psi should be at least 40. You can measure this yourself with a pressure gauge. If it is lower than 40, you may need to consider installing booster pumps.
You can test your home/feed water pressure by finding a water spigot that is close to where the water main enters your household. Attach the pressure gauge, turn on the water, and check the display on the gauge for the psi.
3. Clogged Filters May Need Replacing
Pre-filters will, over time, become clogged with debris, sediment, and other impurities like scale. It is of utmost importance to keep up with your system maintenance and filter replacement schedule to prevent this from happening. If the filters are clogged, insufficient water will flow through.
4. Clogged RO Membrane May Need Replacing
Same goes for your RO membrane. Clogged pre-filters may also lead to clogged membranes, reducing how much water is able to move through them. Make sure to replace your RO membrane on time so the water is going into the tank and not just down the drain.
5. Kink in RO System Tubing
While kinks can be fun, they are not when it comes to your RO system. If there are kinks or bends in your tubes, the water may not flow at optimal pressure to be filtered and stored in the tank. Visually check for any issues to straighten out.
6. Improperly Pressurized Bladder Tank
If the pressure in your RO tank is too high, it’s going to mean less room for water to be stored in it. If the pressure is too low, that’s not going to work either. You will need to empty the tank and reset the psi using a compressor or bicycle tire pump.
7. Ruptured Tank Bladder
This will require your entire tank to be replaced. If you repressurize the tank and it fails again after a couple of days, it is a good indicator your bladder tank has ruptured.
8. Shut Off Leak Detector
If your system is equipped with a shut of leak detector, it will turn off when a leak is detected. Check to see what has triggered this, and then reset the leak detector.
9. High Water Usage
If you have been using more water than your RO system can make, then your tank will be empty and won’t have time to fill. You may want to consider using less RO water or increasing the size of your system.
Further Reading:
10. Airlock
Changing the filters and membranes in your system can sometimes trigger an airlock, which is trapped air where it shouldn’t be. If this happens, close the storage tank valve and open the RO faucet to drain.
11. Low-Flow RO System
Your RO system may be too small or not provide enough pressure to counter the backpressure of the storage tank. Flow rate can be affected by the quality of your feed water, the age/condition of your system’s components, and the water supply’s pressure.
If you have any questions about RO tank pressure please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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