R.O Water Tank

01 Jun. 18

Reverse Osmosis Tank Trouble Shooting

Reverse Osmosis Tank Trouble Shooting

The air tank pressure must always be properly set for a Reverse Osmosis system to work properly.  As Reverse Osmosis systems operate on the hydraulics of the water, the tank must have the air pressure accurately set.  The tank’s air pressure  will work in conjunction with the incoming water pressure to operate the non electric, hydraulic water pressure.   A RO system will not function properly without the tank’s air pressure set correctly.  Also, you cannot properly diagnose an RO system’s problems until the air pressure in the tank is confirmed.

If you can only get a few glasses of water at a time empty tank air pressure is the first thing to check.  Low storage capacity in the tank is usually the result of an under inflated tank.   Systems with under inflated tanks can continue to run too long and quickly foul a membrane, requiring membrane replacement.   It also depletes carbon filters and plugs sediment prefilters too quickly.
Systems that continue to run can also be in need a Replacement Flow Restrictors.

Symptoms of RO tank low air pressure or bladder failure:

*System Runs Too Much
*Low Dispensing Pressure From Faucet
*Not Much Water In Tank
*If the tank is still heavy like a small bowling ball after opening the
faucet and allowing all of the water to drain from the tank.

To keep your system operating correctly, check the tank pressure each time you change the filters.

Other problems can occur if the tank is not providing the correct pressure to the system (7 PSI when empty of water).   The membrane and filters will not last as long, being prematurely exhausted or fouled.   It is important to monitor the pressure and correct it if it is not maintaining the correct pressure.
Proper tank pressure (7 PSI) must be maintained for the hydraulic functions of the water to work correctly within the RO system.   Tank bladders can lose air pressure just like a tire looses air pressure.  We suggest a SPECIALLY CALIBRATED AIR PRESSURE GAUGE to monitor your system’s air tank pressure to help insure proper system operation.


1.   Turn off the RO system’s inlet water line.
2.   Open the faucet and allow the water to run until the flow stops.  Close the faucet.
3.   Turn off the tank valve.
4.   Lift the tank.  Is it heavy like it has water in it?  About the weight of a bowling ball? (If the answer is yes, replace the tank)
5.   Check the air pressure of the tank.  There is an air stem on the tank similar to the ones on a tire.  They are usually covered with a rubber or plastic cap to protect them.  You must remove the cap to expose the air stem.
6.   Inflate or deflate tank to reach the desired 7 PSI air pressure.  You can use a standard air pump similar to a bike pump or compressor.  Easy does it with the compressor, this is a low pressure system.  Do not over inflate and damage the air bladder.
7.  Open the tank valve.
8.   Open the inlet water valve.
9.  Allow the tank to fill.  This may take a few hours.  Once filled, see if the system now operates correctly after you corrected the air pressure.  If not, see the following:


The other problem is that Reverse Osmosis tank bladders frequently fail, requiring replacement of the tank.   If the bladder in the tank starts to leak  water into the air side of the bladder,  the tank will have to be replaced.
Open the faucet and drain all of the water from the tank.
Pick up the tank.  If the tank feels heavy like it is full even though you can’t get water out of the faucet, the bladder is ruptured.  Also, as this happens the air stem sometimes may be wet, or the air valve may even rust from water that passed to the air side of the bladder.   Lift the tank when empty and hold it upside down so that the air stem is at the very lowest point on the tank.  Then discharge some air from the air valve.  Did you get any water?  If so, the tank must be replaced.  Another problem is that the air valve may leak air just like a bike or car tire.   Air valves leaking air is actually is a very common failure.  See Replacement RO Tanks.