The three ways to pressurize a water tank

A water tank loses pressure when air escapes, sediment clogs the outlet, or the tank straightforward sits unused for a while. You can restore pressure by adding air back into the tank, clearing the outlet valve, or installing a pressure pump if your home's natural water pressure is too low. The method you choose depends on whether your tank is a pressure tank (sealed, with an air pocket inside) or a storage tank (open-top or vented), and whether you have a pump system already in place.

Most homes with well water use a pressure tank. City water homes rarely need to pressurize a tank unless they have added one for storage or backup. The steps differ between these two types, so identify which you have before you start.

Key Takeaways

  • A pressure tank needs air added back through the air valve on top, using a bicycle pump or compressor, when the pressure gauge reads below the pump's cut-in setting.
  • Check the air pressure in your tank when it is empty (no water inside) — it should be 2 pounds per square inch (PSI) below your pump's cut-in pressure, usually around 28 PSI for a 40/60 system.
  • If your tank has lost pressure repeatedly, the internal bladder or diaphragm may have failed and the tank will need to be replaced.
  • A storage tank without a pump system cannot be pressurized — you need to install a pressure pump to boost water pressure throughout your home.
  • Sediment blocking the outlet valve is the most common reason pressure seems low; draining and flushing the tank often restores normal flow.

How to add air to a pressure tank

A pressure tank holds both water and air. The air pushes down on the water and forces it out through your pipes when you open a faucet. Over time, the air dissolves into the water or leaks out through the air valve, and pressure drops. Adding air back is the fastest fix.

First, turn off the pump at the pressure switch or breaker. Drain the tank completely by opening the lowest drain valve and letting water run until nothing comes out. This step is critical — if water is still in the tank, you will damage the pump or create a safety hazard when you add air.

Locate the air valve on top of the tank. It looks like a bicycle tire valve. Use a tire pressure gauge to check the current air pressure inside. Write down the number. Next, check your pump's cut-in pressure — this is printed on the pressure switch, usually a label on the side of the tank or near the electrical box. A common setting is 40/60, meaning the pump turns on at 40 PSI and off at 60 PSI.

The air pressure in the tank should be 2 PSI below the cut-in pressure. For a 40/60 system, aim for 38 PSI. Use a bicycle pump, hand pump, or air compressor to add air until the gauge reads the target number. Do not overfill — too much air will damage the tank's internal bladder. Once you reach the target, close the air valve and refill the tank by turning the pump back on.

Clearing a clogged outlet valve

Sediment and mineral buildup inside the tank can block the outlet valve, making it feel like pressure is low when water is actually still in the tank. The water straightforward cannot flow out fast enough. Flushing the tank usually solves this.

Turn off the pump and open the drain valve at the bottom of the tank. Let water run for several minutes — longer if the water comes out cloudy or brown. Close the drain valve. Open a faucet in the house and turn the pump back on. If water now flows normally, the blockage is cleared. If pressure is still low, the problem is air pressure, not sediment.

If sediment keeps returning, your well water is unusually hard or your tank is old and corroding inside. In that case, install a sediment filter on the inlet line before the tank. This catches particles before they enter and reduces how often you need to flush.

Installing a pressure pump for a storage tank

A storage tank without a pump system cannot hold pressure on its own. If you have added a tank to your home for backup water or to increase volume, and you want pressurized water throughout the house, you must install a pump.

A centrifugal pump is the most common choice for this job. It mounts on the outlet line of the tank and pushes water into your home's pipes at a set pressure. You will also need a pressure switch (which turns the pump on and off based on pressure), a pressure gauge (to monitor the system), and a small pressure tank to cushion the pump and prevent it from cycling on and off constantly.

This is not a straightforward DIY job if you have no plumbing experience. The pump must be wired to a dedicated circuit, the pressure switch must be calibrated to your desired pressure, and all connections must be watertight. Hire a plumber who works with well systems or pump installations. The cost varies widely depending on pump size and your local labor rates, but expect to budget for the pump itself, the pressure tank, electrical work, and plumbing connections.

When the tank bladder has failed

A pressure tank contains a rubber bladder or diaphragm that separates the air from the water. If this bladder tears or develops a hole, air leaks out constantly and pressure will not hold. You will notice the pump running more often than usual, or pressure dropping within hours of the pump shutting off.

To test whether the bladder has failed, drain the tank completely and check the air pressure. If it reads zero or very close to zero, and you know the tank had air in it before, the bladder is likely torn. Some tanks allow you to replace the bladder without replacing the whole tank, but this requires draining, depressurizing, and opening the tank — a job best left to a plumber.

If the tank is more than 10 years old, replacement is usually cheaper than repair. A new pressure tank costs less than the labor to rebuild an old one. If your tank is newer and the bladder fails, contact the manufacturer — some offer warranties that cover defects.

Checking your pump's pressure settings

If you have added air to the tank and cleared sediment but pressure is still low, the pump's pressure switch may be set too low or may have drifted out of adjustment. The pressure switch controls when the pump turns on and off.

Look at the pressure switch — it is a small box mounted on or near the tank with two adjustment nuts on top, usually labeled with + and − symbols. The lower nut controls the cut-in pressure (when the pump starts), and the upper nut controls the differential (the gap between cut-in and cut-out). Do not adjust these yourself unless you are comfortable working with electrical equipment and understand your system. Turning the wrong nut can damage the pump or create unsafe pressure.

If you suspect the switch is out of adjustment, call a well service technician. They can test the switch, adjust it to the correct pressure for your home, and verify that the pump is working as designed. This usually costs less than replacing the tank and takes an hour or two.

Frequently Asked Questions

What PSI should my pressure tank be at?

The air pressure in an empty tank should be 2 PSI below your pump's cut-in pressure. For a 40/60 system, that is 38 PSI. For a 30/50 system, it is 28 PSI. Check the label on your pressure switch to find your system's setting, then subtract 2.

Can I use a regular air compressor to pressurize my tank?

Yes, a standard air compressor works fine. Use the tire valve on top of the tank just as you would fill a bicycle tire. Check the pressure with a tire gauge and stop when you reach your target. Do not use an air compressor that is dirty or oily — it can contaminate your water.

Why does my pressure tank lose air so quickly?

The internal bladder or diaphragm is likely torn or leaking. Air escapes through the hole and pressure drops within hours or days. Draining the tank and checking the air pressure when empty will confirm this. If it reads zero, the bladder has failed and the tank needs replacement or repair.

Do I need a pressure tank if I have city water?

No. City water arrives at your home already pressurized by the municipal system. You only need a pressure tank if you have a well, or if you have added a storage tank and want pressurized water from it. City water homes do not pressurize tanks.

How often should I check my tank's air pressure?

Check it once a year, ideally in the fall before winter. If you notice the pump running more often than usual or pressure dropping suddenly, check it right away. Most tanks lose a small amount of air over time, so an annual check and top-up is normal maintenance.