Why and When to Drain Your Pressure Tank

Draining a well water pressure tank is routine maintenance that takes 30 minutes to an hour. You drain it to remove sediment that collects at the bottom, to replace the air charge inside the tank, or to repair or replace the tank itself. Most homeowners need to do this once every few years, though tanks in areas with hard water or high sediment may need it more often.

The tank holds both water and compressed air. Over time, water absorbs the air charge, and sediment settles to the bottom. When the air charge weakens, the pump cycles on and off more frequently, wearing it out faster. Draining removes that sediment and lets you restore the air pressure to the correct level for your system.

You will know it is time to drain if the pump is running constantly, if you hear the pump kick on every few minutes even when no water is running, or if you see rust-colored water coming from your taps. These are signs the tank needs attention.

Key Takeaways

  • Turn off the pump at the breaker and open the lowest faucet in your house to release pressure before you open the tank drain valve.
  • Attach a hose to the drain valve at the bottom of the tank and run it to a floor drain, sump pump, or outside away from your foundation.
  • Open the drain valve fully and let the tank empty completely, which usually takes 10 to 20 minutes depending on tank size.
  • After draining, close the drain valve, turn the pump back on, and let the tank refill before checking the air pressure with a tire gauge at the air valve on top.
  • The correct air pressure is usually 2 pounds per square inch (psi) below your pump's cut-in pressure, which you can find in your pump manual or on the pressure switch.

Shut Off Power and Release System Pressure

Before you touch the tank, turn off power to the pump. Find the breaker that controls the pump — it is usually labeled in your electrical panel — and switch it to the off position. This prevents the pump from running while the tank is open and pressurized.

Next, release the pressure in the system. Open the lowest faucet in your house (usually a basement sink or outdoor spigot) and let water run until it stops. This drains the pressure from the lines. You should hear a hiss or feel air coming out as the pressure releases. Once the water stops flowing, the system is depressurized and safe to open.

Attach a Hose to the Drain Valve

Look at the bottom of your pressure tank. You will see a small valve with a handle or bolt head — this is the drain valve. Attach a garden hose to this valve if it has a threaded outlet, or position a bucket underneath if it does not. If you are using a hose, run it to a floor drain, a sump pump pit, or outside at least 10 feet away from your foundation to avoid water damage.

Make sure the hose is find before you open the valve. If the tank is in a basement or crawlspace, a floor drain is ideal. If you have no floor drain, a 5-gallon bucket works, though you will need to empty it several times as the tank drains. Outside drainage is acceptable but avoid letting water pool near your foundation or septic system.

Open the Drain Valve and Let the Tank Empty

Turn the drain valve handle counterclockwise or unscrew the bolt head slowly. Water will begin to flow out. Open it fully to speed up the draining process. The tank will empty in 10 to 20 minutes depending on its size — a typical residential tank is 42 to 80 gallons.

You may see sediment, rust, or discolored water come out first. This is normal and is exactly why you are draining the tank. Let it run until clear water comes out and then stops. Do not close the valve until the flow has completely stopped and no more water drips out.

Close the Valve and Refill the Tank

Once the tank is empty, close the drain valve by turning the handle clockwise or screwing the bolt head back in. Tighten it firmly but do not over-tighten, which can strip the threads. Disconnect the hose if you used one.

Now turn the pump back on at the breaker. The pump will run and refill the tank with water. You will hear the pump running and feel pressure building in the lines. Let it run until the pump shuts off on its own — this means the tank has reached its cut-out pressure and is full. This usually takes 5 to 10 minutes.

Check and Adjust the Air Pressure

Once the tank is full and the pump has shut off, check the air pressure inside the tank. Look for the air valve on top of the tank — it looks like a tire valve on a car. Use a tire pressure gauge to check the pressure. straightforward press the gauge onto the valve stem and read the number.

The correct air pressure is usually 2 psi below your pump's cut-in pressure. For example, if your pump turns on at 40 psi, the air pressure should be 38 psi. You can find your pump's cut-in pressure in your pump manual, on the pressure switch label, or by calling your pump installer. If the pressure is too low, use a bicycle or electric pump to add air until you reach the correct level.

If the air pressure keeps dropping after you refill it, the tank's internal bladder (a rubber membrane that separates air from water) may be damaged and the tank may need replacement. A tank that loses air pressure repeatedly cannot maintain steady water pressure and will cause the pump to cycle too often.

When to Call a Professional

If you are not comfortable working with pressurized systems, or if you cannot locate the drain valve or air valve, contact a well service company. They can drain the tank, check the air pressure, and replace the tank if needed. The cost is typically $150 to $300 for a service call plus parts.

You should also call a professional if the pump does not shut off after the tank refills, if water sprays from the air valve, or if you cannot get the air pressure to hold steady. These are signs of internal tank failure or a problem with the pump or pressure switch that requires professional diagnosis.

Frequently Asked Questions

How often should I drain my pressure tank?

Most tanks need draining every 2 to 3 years as part of routine maintenance. If you have hard water or high sediment, you may need to drain it annually. If you notice the pump running constantly or cycling frequently, drain it right away regardless of the schedule.

Can I drain the tank while the pump is running?

No. Always turn off the pump at the breaker before opening the drain valve. A running pump will pressurize the tank and force water out with force, which is dangerous and makes the job harder. Turning off the pump and releasing pressure first is essential.

What should I do if no water comes out when I open the drain valve?

The valve may be clogged with sediment. Try closing it and opening it again slowly. If water still does not flow, the valve itself may be stuck or blocked. You may need to replace the drain valve, which is inexpensive and takes 15 minutes. A well service company can do this if you are not comfortable with it.

Is it normal to see rust or brown water when draining?

Yes. Rust and sediment naturally collect at the bottom of the tank over time, especially in areas with iron in the water. This discolored water is why you drain the tank. Once it runs clear, the sediment has been removed and the tank is clean.

What happens if I do not drain my pressure tank?

Sediment will continue to build up, the air charge will weaken, and your pump will run more often and wear out faster. You may also notice reduced water pressure or discolored water at your taps. Regular draining extends the life of both the tank and the pump by 5 to 10 years.