What you are checking and why it matters
A water pressure tank holds pressurized air and water to keep your home's water system running smoothly between pump cycles. Over time, the air charge inside the tank drops, the tank rusts, or the bladder (the rubber membrane separating air from water) fails. Checking your tank tells you whether it is still doing its job or whether you need repair or replacement.
Most homeowners never look at their tank until water pressure drops noticeably or the pump runs constantly. By then, the tank has usually been failing for weeks. A quick check every year or two catches problems early, when they are cheaper to fix.
Key Takeaways
- Check your tank's air pressure with a tire gauge on the air valve at the top — it should match the pressure reading on your pressure switch, usually 30 to 40 psi.
- If air pressure is low or zero, the tank's bladder has likely failed and the tank needs replacement.
- Look for rust, dents, or water pooling under the tank, all signs the tank is deteriorating and should be replaced soon.
- Listen for the pump running constantly or water pressure dropping suddenly — both point to a tank problem that needs attention within days.
Checking air pressure with a tire gauge
The most direct check is measuring the air pressure inside the tank. You will need a tire pressure gauge — the same tool used for car tires, available at any hardware store for under ten dollars. Turn off power to your pump before you start.
Locate the air valve on top of the tank. It looks like a car tire valve and is usually a small metal stem sticking up. Remove the plastic cap. Press the tire gauge onto the valve stem firmly until it seats — you should hear a small hiss of air. Read the pressure number on the gauge. Write it down.
Compare this reading to your pressure switch, a small box mounted on the pipe near the tank. It has two numbers on it, usually something like "30/50" or "40/60". The first number is the pressure at which the pump turns on; the second is the pressure at which it turns off. Your tank's air pressure should be about 2 psi below the pump-on number. If your switch reads 30/50, your tank should have roughly 28 psi of air.
If the gauge reads zero or very low (more than 5 psi below what it should be), the tank's internal bladder has failed. Air has escaped into the water side of the tank, and the tank can no longer cushion pressure swings. Replacement is the only fix.
What to look for when you inspect the tank itself
Rust and corrosion are the most visible sign of trouble. Look at the tank's exterior. If you see orange, brown, or white crusty spots, the steel is corroding from the inside out. Small surface rust may not require when ready action, but heavy rust means the tank is thinning and will eventually leak. Plan to replace it within the next year.
Check for water pooling or dripping underneath the tank. Even a slow drip means the tank is leaking and losing water pressure. This usually happens at a seam or weld and cannot be repaired — the tank must be replaced.
Look for dents or bulges in the tank's sides. A small dent from bumping is usually harmless, but a bulge (the tank swelling outward) means internal pressure is too high or the bladder is failing. A severely dented tank may have a weakened wall and should be replaced.
Feel the tank's temperature. A tank that is hot to the touch (warmer than room temperature) means the pump is running frequently and pressure is not holding. This points to a failing bladder or a slow leak.
Signs your pump and pressure system are struggling
If you cannot access the tank easily or do not have a tire gauge, listen to how your pump behaves. A pump that runs constantly or cycles on and off every few seconds is a classic sign the tank is not holding pressure. The pump should run for a minute or two, then stay off for at least several minutes while you use water. If it is running almost all the time, the tank has lost its air charge.
Notice whether water pressure drops suddenly when you turn on a faucet or shower. Normal pressure should hold steady. If it drops sharply and then builds back up slowly, the tank is not cushioning the system properly. This usually means the bladder has failed.
Pay attention to water sputtering from faucets or showerheads. Air in the water line is often a sign the tank is pulling air into the system because the water level inside has dropped too low. This happens when the bladder fails and water mixes with the air side.
When to refill the air charge yourself
If your air pressure is low but not zero, you may be able to refill it yourself without replacing the tank. Turn off the pump. Use an air compressor (the kind at a gas station or a small portable one) to add air through the valve on top. Add air slowly until the pressure matches what your pressure switch requires — usually 28 to 40 psi depending on your system.
Turn the pump back on and check your water pressure at a faucet. If pressure holds steady and the pump cycles normally, the refill worked. However, if the pressure drops again within a few days or weeks, the bladder is leaking and refilling is only a temporary fix. You will need to replace the tank.
Do not overfill. Adding too much air can damage the bladder or cause the pressure relief valve to open and waste water. If you are unsure of the correct pressure, call a plumber or check your tank's label — most tanks have the recommended air pressure printed on them.
Understanding what the numbers mean
Your pressure switch has two numbers because the system is designed to work within a range. If your switch reads 30/50, the pump turns on when pressure drops to 30 psi and turns off when pressure reaches 50 psi. The tank stores water at high pressure so the pump does not have to run every time you open a faucet.
The air inside the tank is what creates that cushion. As you use water, pressure drops. When it hits 30 psi, the pump kicks in and refills the tank. The air compresses, pressure rises, and at 50 psi the pump shuts off. If the air charge is gone, the tank fills with water instead of maintaining that air cushion. The pump then has to run constantly to maintain pressure.
Different homes have different pressure ranges. Older systems often run 20/40 psi. Newer systems might run 40/60 psi. Check your switch to know what your system needs. The tank's air pressure should always be about 2 psi lower than the pump-on number.
When to call a plumber
If your air pressure is zero or very low and refilling does not hold, the tank needs replacement. This is not a repair you can do yourself — the tank must be drained, disconnected, and a new one installed and pressurized. A plumber will also check your pressure switch and pump to make sure they are working correctly.
If you see rust, water pooling, or bulges, or if your pump is running constantly and you cannot find the cause, call a plumber. These are signs the tank is failing and replacement is the safest option. Waiting until the tank fails completely can damage your pump and leave you without water pressure.
A new pressure tank typically costs between $300 and $800 installed, depending on size and your location. Catching a failing tank early means you can plan for the replacement rather than facing an emergency repair.
Frequently Asked Questions
How often should I check my water pressure tank?
Check it once a year if you have a well system, or every two years if you are on municipal water with a tank for pressure regulation. If you notice changes in water pressure or hear the pump running more often, check it when ready. A quick check takes five minutes and can catch problems before they become expensive.
Can I add air to the tank myself if the pressure is low?
Yes, if you have an air compressor and know the correct pressure for your system. Turn off the pump, add air slowly to match your pressure switch's lower number minus 2 psi, then turn the pump back on. If pressure drops again within days, the bladder is leaking and the tank needs replacement.
What does it mean if water is sputtering from my faucets?
Sputtering usually means air is in the water line, often because the tank's bladder has failed and water level inside is too low. It can also happen after you drain the system for repairs. Run the faucet for a few minutes to purge the air. If sputtering continues, have the tank checked.
Is a water pressure tank the same as a water heater?
No. A pressure tank regulates water pressure in your plumbing system. A water heater warms the water. Some systems have both — the pressure tank is usually larger and mounted separately, often in a basement or utility room. Check your tank's label to confirm what you have.
What happens if I ignore a failing pressure tank?
The pump will run constantly to maintain pressure, wearing it out faster and raising your electric bill. Eventually the pump may overheat and fail. You may also lose water pressure suddenly if the tank ruptures. Replacing a tank costs less than replacing a pump, so addressing it early saves money.