What a bladder tank does and when it needs replacing
A bladder tank is a metal pressure vessel with a rubber bladder inside that stores water under pressure. When you turn on a faucet, the tank releases that stored water so your pump doesn't have to start every single time. The rubber bladder eventually cracks or loses its ability to hold air, usually after 5 to 15 years depending on water quality and how often the system cycles. When it fails, your pump runs constantly, pressure fluctuates wildly, or you lose water pressure altogether.
Replacing a bladder tank is a job most homeowners can do with basic tools, though it involves working with pressurized water and air. If you're not comfortable with the steps or your tank is larger than 20 gallons, calling a well technician is the safer choice. The tank itself costs $150 to $500 depending on size; labor runs $300 to $600 if you hire someone.
Key Takeaways
- Turn off power to the pump and drain the system completely before opening the tank.
- The air charge inside the tank must be released through a valve before you disconnect it.
- New bladder tanks come precharged with air at the factory, but you should verify the pressure matches your system's requirements.
- Reconnecting the tank requires tightening the connection hand-tight first, then using a wrench to avoid over-tightening and cracking the fitting.
- After installation, you will need to restore air pressure and refill the system before the pump can operate normally.
Gather your tools and materials before you start
You will need an adjustable wrench or two, a socket set, a tire pressure gauge (or an air pressure gauge rated for 0–100 psi), a bicycle pump or small air compressor, a bucket or wet/dry vacuum to catch water, and a garden hose if your drain is far from the tank. Wear work gloves and safety glasses because water under pressure can spray unexpectedly.
Before you buy a replacement tank, write down the size of your current tank (usually stamped on the nameplate—look for "20 gal," "30 gal," etc.) and the pressure setting of your system. You can find the pressure setting on the pressure switch, a small box mounted near the tank with two numbers on it (for example, "40/60" means the pump turns on at 40 psi and off at 60 psi). Buy a replacement tank of the same size and have the shop precharged it to match your system's cut-in pressure—usually 2 psi below the pump-on setting.
Turn off power and release all pressure from the system
Switch off the breaker that powers your well pump at the electrical panel. Do not skip this step; a pump can start unexpectedly and cause injury or damage. Wait a few minutes for any residual power to dissipate.
Next, open the lowest faucet in your house (usually a basement or outdoor spigot) and let water run until it stops. This drains the tank and the lines. Then locate the air valve on top of the tank—it looks like a tire valve—and use your tire pressure gauge to slowly release the air charge. You should hear a hiss as the air escapes. Once no more air comes out, the tank is safe to disconnect.
Disconnect the old tank from the pump and plumbing
Place a bucket or wet/dry vacuum under the connection where the tank attaches to the pump line. Using two wrenches—one to hold the fitting on the tank and one to turn the nut on the line—slowly loosen the connection. Water will drip out; this is normal. Once the nut is loose enough to turn by hand, unscrew it the rest of the way and set the old tank aside.
If the tank is bolted to the floor or wall, unbolt it and carefully move it out of the way. Bladder tanks are heavy (a 20-gallon tank weighs about 40 pounds when empty), so get help if you need it. Inspect the connection fitting on the pump line; if it looks corroded or damaged, clean it with a wire brush or replace it before installing the new tank.
Install the new tank and reconnect the plumbing
Position the new tank in the same location as the old one. If it came with mounting brackets, install them now. Check that the air valve on top is accessible and not blocked by pipes or walls.
Thread the connection fitting by hand first to make sure it is going in straight and not cross-threading. Once it is hand-tight, use two wrenches again—one to hold the fitting on the tank and one to turn the nut on the pump line—to tighten it snugly. Do not over-tighten; you are aiming for firm resistance, not maximum force. Over-tightening can crack the fitting or strip the threads.
Charge the tank with air and refill the system
Use your tire pressure gauge to check the air pressure in the new tank. It should read the cut-in pressure of your system (for example, 38 psi if your pressure switch is set to 40/60). If the pressure is too low, use a bicycle pump or small air compressor to add air until it matches. If it is too high, use the valve to release a little air. Getting this right prevents the pump from cycling too often or the tank from not filling properly.
Once the air charge is correct, turn the breaker back on to power the pump. Open the lowest faucet again and let the pump run until water flows steadily and no more air sputters out. This refills the tank and removes air from the lines. Close the faucet and listen to the pump; it should stop once the tank reaches the cut-off pressure. If the pump runs continuously or pressure drops quickly, turn it off and check that all connections are tight and the air valve is sealed.
Test the system and watch for leaks
Turn on several faucets around the house and watch the pressure gauge on the tank. Pressure should hold steady while water flows and then rise again once you close the faucets. If pressure drops suddenly or the pump starts and stops rapidly, the air charge may be wrong or a connection may be leaking.
Check all the connections you tightened with a wrench. If you see water dripping, tighten the nut a quarter turn at a time until the drip stops. If tightening does not help, turn off the pump, drain the system again, disconnect the fitting, wrap the threads with plumber's thread seal tape (also called PTFE tape), and reconnect it. Run the system for an hour and monitor the pressure gauge; it should remain stable.
When to call a professional instead
If your tank is larger than 30 gallons, the connection is corroded or stuck and will not budge, or you are not confident working with pressurized systems, hire a well technician. They have the tools to safely disconnect stubborn fittings and can test your system's pressure switch and pump to make sure everything is working together correctly.
Also call a professional if, after installation, the pump will not turn on, pressure will not build, or water comes out of the air valve when you open a faucet. These signs point to a problem with the pressure switch, pump, or check valve that is beyond a tank replacement.
Frequently Asked Questions
Can I replace a bladder tank without draining the whole system?
No. The tank is under pressure, and opening it without draining will spray water everywhere and can injure you. Always turn off the pump, open the lowest faucet, and release the air charge through the valve before disconnecting anything.
What if the new tank does not come precharged?
Some tanks ship empty. Before you install it, use a tire pressure gauge to check the air pressure inside. If it reads zero, use a bicycle pump or small air compressor to charge it to your system's cut-in pressure (usually 2 psi below the pump-on setting). Do this before you connect it to the pump line.
How do I know if my pressure switch setting is 40/60 or something else?
Look at the small box mounted on or near the tank. It has two numbers printed on it or stamped into the cover. The first number is when the pump turns on; the second is when it turns off. If you cannot find it or it is not labeled, ask your well technician or check your system's original paperwork.
Is it normal for the pump to run a long time after I install the new tank?
Yes, the first time. The pump needs to refill the tank and pressurize it to the cut-off setting. This can take 10 to 20 minutes depending on your pump's flow rate and tank size. After that, the pump should cycle on and off normally as you use water.
What should I do if water leaks from the connection after I tighten it?
Turn off the pump, drain the system, and disconnect the fitting. Wrap the male threads (the part going into the tank) with plumber's thread seal tape, wrapping clockwise three to four times. Reconnect and tighten with two wrenches. If it still leaks, the fitting itself may be damaged and needs replacement.