How to Air Charge a Waterlogged Pressure Tank

There are 3 types of well pressure tanks. You will either have the old galvanized (air-over-water) pressure tank or the more modern bladder or diaphragm pressure tank. More on that in this post.

With bladder and diaphragm pressure tanks, there is a clear barrier between the water and the air. As a result, the tanks will hardly ever be waterlogged unless there the bladder or diaphragm has ruptured, in which case the tank would need to be replaced.


In a galvanized pressure tank, there is no barrier between the water and the compressed air. The compressed air occupies the top section of the tank where it is compressed by the water. This is why these tanks are also known as air-over-water pressure tanks.

With time, the compressed air dissolves into the water and as a result the water occupies even more space in the tank. Eventually the tank will completely be filled with water and at that time we say the tank is waterlogged.

This signs of a waterlogged pressure tank are a short-cycling well pump, fluctuating water pressure and a tank that is cold from top to bottom. If the pressure tanks is cold at the top and sounds solid when tapped, it means water was displaced the air.

A short-cycling pump is bound to fail prematurely if the pressure tank is not charged as soon as possible.

To air charge a waterlogged pressure tank, you will need turn off the well pump, shut off the house water supply valve then completely drain the tank. Fill the tank with 25 psi of air and then turn on the pump to fill the tank with water then open the shut off valve.

Although bladder-type pressure tanks cannot be air charged when waterlogged, the pressure in the tanks will drop with time (just like your car tires) and will need to be recharged. Ideally, the air pressure in the tank should be 2 psi less than that of the cut-in pressure.

How to Air Charge an Air-Over-water Pressure Tank

As mentioned above, a galvanized pressure tank will need to be recharged from time to time. If you are not sure how to do it, this is how to add air into an old air-over-water pressure tank:

1. Turn off the Well Pump

Since you will need to empty the tank in order to pump in air, you must first turn the well pump off. Leaving the pump running with no water in the tank will have the pump pumping dry at some point, which is the easiest way to kill it.

Dash to your electrical panel and look for the breaker marked “Well Pump”. Flip it to the off position. You can as well unplug the pump from the electrical outlet.

2. By-Pass Filtering Equipment

Before draining the tank, you will need to by-pass or turn off all water filtering equipment. This includes equipment like the water softener, reverse-osmosis equipment, iron filter and others.

Draining the tank without by-passing them will result in them being clogged up by sediment. Remember that there is a lot of debris at the bottom of your pressure tank as well as inside the water pipes.

3. Drain the Tank

  • Open any faucet that does not have a filtration screen. If you look at the tip of your kitchen/bathroom faucet, you will notice that the faucet spout has a small attachment called an aerator. You want to avoid such a faucet since the sediment can badly clog the aerator.
  • Let the water flow out until the pressure in the tank drops to 0.
  • With the faucet still open, turn on the air compressor. The air from the compressed will flush out any water still left in the tank.

Sometimes the opening where the pressure tank’s air inlet valve is installed could be clogged by mineral deposits and air won’t just flow in. If that is the case, use a pair of pliers or wrench to disconnect the valve and unblock the hole with a screwdriver. Connect the valve back.

4. Recharge the Tank

  • When much of the water has been evacuated from the pressure tank, turn off the main shut off valve from the pressure tank to your house plumbing.
  • Continue pumping in air into the pressure tank until you have 25 psi (pounds per square inch) of air pressure.
  • Turn off the air compressor and switch on the well pump.
  • Open the main shut off valve to the house plumbing and let water run out until clear.
  • Power back the filtering system/equipment.

And basically that is how to air charge a waterlogged galvanized pressure tank. You will need to do this all over again when the water pressure in your house reduces. You do not have to wait until the tank is completely waterlogged in order to recharge it.

How to Air Charge a Bladder/Diaphragm Pressure Tank


If you have a bladder or diaphragm pressure tank and your well pump is coming on and off frequently than usual, you may need to air charge it. Remember that if the air pressure in the tank drops too much, it reduces you pressure tank’s drawdown and hence the short-cycling pump.

There are 2 things that you will need to do before charging your bladder/diaphragm pressure tank. These are:

  • Make sure that the tank is not waterlogged due to a ruptured bladder/diaphragm.
  • Determine your pressure switch’s cut-in and cut-out pressure.

To check if the pressure tank bladder is ruptured, remove the air inlet’s cap and press the piston down in a bid to bleed off some air. If water comes out instead of air, the bladder has ruptured and will need to be replaced.

The cut-in pressure is the lower pressure setting when the pressure switch activates the motor to start pumping water into the tank. On the other hand, the cut-off pressure is the higher pressure settings when the pressure switch turns off the pump.

A pressure switch is the device that turns the well pump on and off with respect to the water pressure inside the tank. It is installed nearer to the pressure tank and has a plastic cap/cover secured by a bolt and wires connected to it.

To determine your cut-in and cut-off pressures, open a faucet in your house and monitor the pressure gauge next to the pressure tank. Notice the pressure at which the pump comes on (cut-in pressure) and the pressure when the pump goes off (cut-off pressure).

There is usually a 20 psi difference between the 2 pressures. You will have a 20/40 psi, 30/50 psi or a 40/60 psi setting.

As I had mentioned earlier, you need to fill you tank with air up to just 2 psi below the cut-in pressure. You however cannot determine the current air pressure in the pressure tank since it is already full of water.

The water in the tank is still compressing the air chamber and the pressure you would get would be erroneous. To get the correct air pressure you would need to first drain the tank.

Before draining the pressure tank, do not forget to turn off the pump at the electrical panel.

To drain the pressure tank, turn off the valve to the house plumbing and open the drain valve at the bottom of the tank. You will need to connect a garden hose to the drain valve and drain the water out into the driveway or anywhere else.

Note: Some pressure tanks do not have a shut off valve from the tank to the house and in that case you will need to bypass or turn off all water filtration systems.

When the tank is completely drained, connect a tire gauge on the pressure inlet valve (at the top of the tank) and check the air pressure.

Start the air compressor (or use a bicycle pump) to add pressure in the air chamber to just under 2 psi of the pressure switch’s cut-in pressure. Turn on the pump and open the shut off valve to the house plumbing.

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