Check your tank pressure with a tire gauge in under a minute
A water pressure tank (also called a pressure tank or bladder tank) holds pressurized water between pump cycles. Over time, the air pressure inside the tank drops, which forces your pump to run more often and wear out faster. You can check the pressure yourself using a tire pressure gauge — the same tool you use for car tires — in about 60 seconds.
Most residential tanks should sit at 2 pounds per square inch (psi) below your system's cut-in pressure. If your pump turns on at 40 psi, your tank should read 38 psi when the system is at rest and the tank is empty. If the reading is much lower, the tank has lost air and needs recharging.
Key Takeaways
- You check tank pressure using a standard tire pressure gauge on the air valve at the top of the tank.
- The reading should be 2 psi below your pump's cut-in pressure — usually 38 psi on a 40 psi system.
- Always turn off the pump and drain the tank completely before checking, so you read air pressure only.
- If pressure is low, the tank can be recharged with an air compressor, or replaced if the bladder has failed.
Locate the air valve on top of the tank
The air valve sits on the very top of the pressure tank, usually under a small plastic or metal cap. It looks identical to a tire valve on a car wheel — a short stem with a slot or hole in the center. The cap may say "air" or have a small picture of air waves.
If you cannot find it, check your tank's manual or look for a label on the tank itself. Some tanks have the valve on the side near the top, but the top is the standard location. Do not confuse it with the water drain valve at the bottom or the pressure gauge port on the side.
Turn off the pump and drain the tank completely
Before you check pressure, you must turn off the pump and release all water from the tank. If water is still inside, your gauge will read water pressure, not air pressure, and the reading will be wrong.
Switch off the pump at the breaker or control switch. Then open the lowest faucet in your house (usually a basement sink or outdoor spigot) and let water run until it stops. This drains the tank. You may hear air hiss out as the tank empties — that is normal. Wait 30 seconds after the water stops to make sure the tank is fully empty.
Unscrew the cap and attach the tire gauge
Remove the plastic or metal cap covering the air valve by turning it counterclockwise by hand. Set it aside somewhere you will not lose it.
Take a standard tire pressure gauge — a stick gauge or digital gauge both work — and press it firmly onto the valve stem. You should hear a small hiss of air as the gauge seats. Hold it steady for 2 to 3 seconds until the reading stabilizes. Write down the number.
Compare your reading to the correct pressure
Your tank pressure should be 2 psi below the pressure at which your pump turns on. Most home systems cut in at 40 psi, so the tank should read 38 psi. Some systems run at 30 psi cut-in (tank reads 28 psi) or 50 psi cut-in (tank reads 48 psi).
You can find your pump's cut-in pressure on the pump's pressure switch, which is usually mounted on the side of the tank or on a pipe near the tank. It will be labeled with two numbers — the lower number is cut-in. If you cannot find it, check your well system's paperwork or call your pump installer.
If your reading is 2 to 4 psi lower than it should be, the tank has lost some air and should be recharged. If it is 10 psi or more below target, the tank has lost significant pressure and needs when ready attention.
Recharge the tank if pressure is low
A tank that has lost pressure can often be recharged using a standard air compressor. Turn off the pump, drain the tank completely (as you did before checking), and use the compressor to add air through the valve until the gauge reads the correct pressure.
Add air slowly — do not blast it in all at once. Check the pressure every few seconds. Once you reach the target, remove the gauge, replace the cap, and turn the pump back on. The system should run normally.
If the tank will not hold pressure and drops again within a few days, the internal bladder has likely failed and the tank will need to be replaced. This is not a repair you can do yourself — call a well pump technician to install a new tank.
Check pressure once or twice a year
A healthy tank should hold its pressure for months. Check it once in spring and once in fall, or whenever you notice your pump running more often than usual. Frequent pump cycling is often the first sign that tank pressure has dropped.
If you live in a very cold climate, check the tank in late fall before freezing weather arrives. Cold can lower air pressure slightly, and you want to know the tank is in good shape before winter.
Frequently Asked Questions
What if I do not know my pump's cut-in pressure?
Look at the pressure switch mounted on or near the tank — it will show two numbers, and the lower one is cut-in. If you cannot find the switch or read it, call your pump installer or a well service company. They can tell you the correct pressure in one phone call.
Can I check pressure while the pump is running?
No. The tank must be empty and the pump off, or you will read water pressure instead of air pressure. Always drain the tank first and wait for the pump to stop.
What happens if tank pressure gets too high?
If you accidentally overcharge the tank, the pump will cycle less often but may not build enough pressure to reach your faucets. Release a small amount of air by pressing the gauge onto the valve briefly, then check again. Aim for 2 psi below cut-in.
Why does my tank pressure keep dropping?
A slow leak in the bladder is the most common cause. If you recharge the tank and it drops again within days, the bladder has failed and the tank needs replacement. A slow loss over several months is normal and just means you need to recharge it periodically.
Do I need a special gauge to check tank pressure?
No. Any tire pressure gauge works — stick gauges are cheap and reliable. Digital gauges are easier to read but cost more. Both give accurate readings on a water pressure tank.