How to Check and Adjust Your Well Tank’s Pressure

Whenever you are experiencing low water pressure from a well and the pump is not the problem, it is always a good idea to investigate the pressure tank. Just like the air in your car tires, the air pressure inside the tank’s chamber will decrease with time and directly impact your water pressure.

Apart from reduced water pressure, when the air pressure inside the chamber decreases, your well pump will come on and off way frequently than it should. That is called short-cycling.


A short-cycling pump will most definitely fail prematurely if the pressure tank problem is not addressed sat enough. This is caused by overheating and wearing out of the motor.

The air pressure inside a well tank should be 2 psi lower than the pressure switch’s cut-in pressure. That means 18 psi if the cut-in pressure is 30 psi, 28 psi if the cut-in pressure is 30 psi and 38 psi if the cut-in pressure is 40 psi.

A pressure switch is the electrical device next to the pressure tank which is covered by a plastic cap. It is responsible for turning the well pump on and off with respect to the water pressure inside the pressure tank.

The cut-in pressure is the pressure switch’s lower pressure setting at which the pump kicks in. Pressure switches have a higher pressure setting also at which they turn the pump off, called the cut-off pressure.

There is usually a 20 psi difference between the cut-in and the cut off pressure. The following are the likely cut-in and cut-off pressure settings on your pressure switch:

  • 20/40 psi
  • 30/50 psi
  • 40/60 psi

You can adjust your pressure switches cut-in and cut-off pressure but you can’t exceed the maximum setting. Doing so will result in a ruptured bladder/diaphragm which means a waterlogged pressure tank. A waterlogged pressure tank will need to be replaced. More on that here.

To check your well tank’s pressure, turn off power to the pump and drain the tank. Connect a pressure/tire gauge on the tank’s air inlet valve and check the reading on the gauge. If needed, pump in more air to just under 2psi of the pressure switch’s cut-in pressure.

If your pressure tank is cold from top to bottom, water comes out when you try to bleed off air or sounds solid when tapped from the bottom to the top, it is waterlogged and will need to be replaced. This is usually caused by a ruptured bladder/diaphragm.

In this article, I will be focusing on bladder/diaphragm pressure tanks, if you still have the old galvanized (air-over-water) pressure tanks check out this post.

Bladder and diaphragm pressure tanks work the same way, just that in bladder tanks there is a balloon-like bladder where the water is held while in diaphragm tanks a rubber diaphragm is installed across the middle of the tank.

How to Check a Well Tank’s Pressure

The following are the steps to follow when checking and adjusting the air pressure in your well tank:

1. Determine your Cut-in Pressure

You need to first know your pressure switch’s cut-in pressure. Remember I mentioned that your pressure tank needs to be set at 2 psi less than the cut-in pressure.

To check your pressure switch’s cut-in pressure, this is what to do:

  • Open a nearby faucet and leave the water running.
  • Dash to where you have the pressure tank and keenly observe the pressure gauge connected to it.
  • Notice the exact pressure when the well pump kicks in. That is your cut-in pressure.
  • Turn off the faucet.
  • Again, check the pressure when the well pump goes off. That is your cut-off pressure.

2. Turn off the Pump

Since you will be draining the tank (meaning pressure will be way lower than the cut-in pressure), you will want to make sure your pump is turned off.  Draining water from the tank with more being supplied by the tank will have you working for eternity.

Dash to your electrical panel and check the breaker marked “Well Pump”. Flip it to the off position. You can as well plug off the pump from the electrical outlet on the wall.

If you have any water filtration equipment in your house, you will also need to turn them off or bypass them before draining the tank to avoid being clogged by sediments.

3. Drain the Tank


So, why do you need to drain the pressure tank? The reason why you want to drain the pressure tank is that the water inside the bladder (or under the diaphragm) is already compressing the air chamber at the top of the tank.

Checking the pressure with the tank full of water will therefore be erroneous since you will end up with the water pressure and not the air pressure. You need to check the pressure when the tank is empty.

Before draining the tank, you should also check if the tank is waterlogged. Tap the bottom of the tank with your arm then the top. The bottom part of the tank should be cold and sound solid when tapped.

Due to the air at the top of the tank, the top half is expected to be warmer and sound hollow when tapped. If however the tank is all cold and sounds solid from top to bottom, it is most likely waterlogged.

Remove the cap on the air inlet valve at the top of the tank and try to bleed off some pressure. If you see water coming out and not air, the tank is waterlogged and will need to be replaced.

  • Turn off water to the house. On the pipe that delivers water from the tank to the house is shut off valve which you need to turn off prior to draining the tank.
  • Connect a garden hose on the boiler drain on the manifold at the bottom of the tank. Direct the end of the garden hose out into the driveway or into a floor drain.

Note: All pressure tanks are not designed the same way. If yours does not have a drain valve at the bottom, you will need to drain it from one of your faucets. Avoid the kitchen or bathroom faucets which have faucet aerators. Those can be badly clogged by the sediment at the bottom of the tank.

  • When the tank is completely drained, turn off the drain valve and disconnect the garden hose.

4. Check the Tank’s Pressure

With the pressure tank completely drained, you can now go ahead and check the air pressure inside it. To do that, you will need a tire gauge.

The air inlet valve at the top of the tank is similar to the one found in bicycle or car tires. It is used for checking the air pressure and also add more pressure should that be needed.

Connect the pressure gauge on the valve and check the reading indicated on the gauge. Compare your results with the cut-in pressure you saw on the pressure gauge at the bottom of the tank.

If the air pressure is too low, you will need to adjust it. As I said, when the pressure in the tank is way lower than the cut-in pressure, the drawdown capacity of your pressure tank will reduce as well.

A pressure tank’s drawdown is the amount of water you will need to draw from the tank from the time the pump goes off to the time the pump kicks in again.

5. Adjust the Pressure

If the pressure in the tank is too low, increasing it is easy. An air compressor is an effortless way of adding more pressure in the tank but in case you don’t have one a bicycle pump will suffice.

Be careful that you do not exceed the cut-in pressure. If you do, you can always bleed off some pressure by pressing down the piston on the air inlet valve.

6. Turn the Pump Back On

When you have checked and adjusted the well tank pressure, turn the pump back on to start filling the tank. Since you will have air in the tank, turn on one faucet to help flush out the air.

Do not forget to turn on the water filtration equipment back on as well.

Adjusting the Pressure Switch

If you would like to adjust the cut-in and cut-off pressure, you will need to do it at the pressure switch. If you remove the pressure switch cover you will see the recommended cut-in and cut-off pressure on its back.

There are 2 springs on the pressure switch compressed on bolts using nuts. One spring controls the cut-in pressure while the other controls the cut off pressure.

To adjust the cut-in and cut-off pressures you will need to compress or release the springs by tightening or loosening the nuts. The only downside to this is that you need to do it with the power switched off.

This means you have to turn the power on and off until you get your desired pressure settings. Attempting to do so with the power on could cause electrical shock.

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