What a pressure switch does and why you might adjust it

A pressure switch is the device that tells your well pump when to turn on and off. It monitors the pressure inside your pressure tank and triggers the pump to start when pressure drops below a set point, then stops it when pressure reaches a higher set point. The difference between these two points is called the pressure differential or cut-in and cut-out settings.

You adjust a pressure switch when your pump is cycling too often (turning on and off rapidly), when it is not building enough pressure to reach your faucets, or when you want to change the overall pressure in your system. Common reasons include a waterlogged pressure tank, a leak somewhere in the line, or straightforward wanting higher or lower water pressure throughout your home.

Most residential well systems run between 30 and 50 pounds per square inch (PSI). The typical factory setting is 30 PSI cut-in and 50 PSI cut-out, meaning the pump starts at 30 and stops at 50. Adjusting this is a straightforward mechanical task that requires only a wrench and a pressure gauge.

Key Takeaways

  • A pressure switch has two adjustment screws: one for the cut-in pressure (when the pump starts) and one for the pressure differential (the gap between start and stop).
  • You must turn off power to the pump and drain the pressure tank before opening the switch to avoid injury and water spray.
  • Adjustments are made in quarter-turn increments, and you should test the system after each small change rather than making large jumps.
  • Most household systems work well between 30 and 50 PSI, and raising pressure above 60 PSI can damage fixtures and seals over time.
  • If the pump cycles rapidly even after adjustment, the problem is usually a waterlogged tank or a leak, not the switch itself.

Locate the pressure switch and identify the adjustment screws

The pressure switch is mounted on or near the pressure tank, usually at the top or side. It is a small cylindrical or rectangular box with two or three wires running into it and a cover held on by one or two bolts. Remove the cover by unbolting it — you will see two adjustment screws inside, sometimes labeled or color-coded.

The upper screw (or the one marked with a plus sign or labeled "cut-in") adjusts the pressure at which the pump starts. The lower screw (or the one marked with a minus sign or labeled "differential") adjusts the gap between cut-in and cut-out. Some switches have a third screw for fine-tuning, but most residential switches use only these two.

Write down the current position of both screws before you touch anything. You can do this by counting the number of turns as you back each screw out, or by taking a photo of the switch with the cover off. This gives you a reference point if you need to return to the original setting.

Turn off power and depressurize the system

Switch off the breaker that controls the pump at your electrical panel. Do not rely on a switch at the pump itself — go to the breaker box. This prevents the pump from starting unexpectedly while you are working.

Next, open a faucet at the lowest point in your house (usually a basement or outdoor spigot) and let water run until it stops. This drains the pressure tank. You can also open the drain valve on the pressure tank itself if one is visible. Wait a few seconds after water stops flowing to may support all pressure has released.

Once the tank is empty, you can safely remove the pressure switch cover. If water drips out, that is normal — have a rag or small bucket ready. Do not proceed until you are certain the system is depressurized, or you risk a sudden spray of water when you open the switch.

Adjust the cut-in pressure (pump start point)

The cut-in screw controls the pressure at which your pump turns on. If your pump is not building enough pressure to reach your faucets, or if you want higher overall pressure, turn the cut-in screw clockwise (to the right) in quarter-turn increments. Each quarter turn typically raises the cut-in pressure by 2 to 4 PSI, depending on the switch model.

If your pump is cycling too often or you want lower pressure, turn the cut-in screw counterclockwise (to the left) in quarter-turn increments. Again, make small changes — do not turn more than one full rotation at a time.

After each quarter turn, close the switch cover, turn the breaker back on, and let the pump run until it stops. Then turn the breaker off again, open a faucet to depressurize, and check the pressure with a gauge attached to the tank. Record the reading and compare it to your target. Repeat this cycle until you reach the pressure you want.

Adjust the differential (the gap between start and stop)

The differential screw controls how much pressure builds up after the pump starts before it shuts off. A typical differential is 20 PSI — if cut-in is 30 PSI, cut-out will be 50 PSI. If your pump is cycling too frequently, increasing the differential can help by allowing the tank to fill more before the pump stops.

Turn the differential screw clockwise to increase the gap (the pump will run longer and build more pressure before stopping). Turn it counterclockwise to decrease the gap (the pump will stop sooner). Again, use quarter-turn increments and test after each change.

A larger differential means the pump runs less often but for longer periods. A smaller differential means the pump cycles more frequently but for shorter bursts. Most systems work well with a 15 to 20 PSI differential, but you can adjust this based on how your system behaves.

Test the system and verify pressure with a gauge

After you have made your adjustments, close the switch cover, turn the breaker back on, and let the pump run through a full cycle. Listen for the pump to start, run for a while, and then stop. The pressure should rise smoothly without the pump cycling on and off rapidly.

Attach a pressure gauge to the test port on your pressure tank (a small valve, usually near the bottom of the tank). Record the pressure when the pump stops — this is your cut-out pressure. Open a faucet and let water run until the pump starts again — the pressure at that moment is your cut-in pressure. The difference between these two readings is your actual differential.

Compare these readings to your target settings. If they are close, you are done. If they are off by more than a few PSI, make another quarter-turn adjustment, depressurize, and test again. It may take two or three cycles to dial in the exact pressure you want.

Common problems and when to stop adjusting

If the pump continues to cycle rapidly even after you have raised the cut-in pressure and increased the differential, the problem is not the switch — it is usually a waterlogged pressure tank or a leak in the line. A waterlogged tank cannot store air properly and cannot cushion pressure changes, so the pump has to run constantly to maintain pressure. A leak drains the tank, forcing the pump to restart frequently.

To check for a waterlogged tank, turn off the pump and listen at the tank. If you hear water sloshing inside, the air bladder has failed and the tank needs to be replaced or re-pressurized by a professional. To check for a leak, turn off the pump, note the pressure gauge reading, wait an hour without using water, and check again. If the pressure has dropped, you have a leak somewhere in the system.

Do not raise the cut-in pressure above 60 PSI on a residential system. Higher pressures can damage rubber seals in faucets, fixtures, and the pump itself, and can cause leaks in older pipes. If you need pressure above 60 PSI, you likely have a tank or pump problem that needs professional attention, not a switch adjustment.

Frequently Asked Questions

What is the difference between cut-in and cut-out pressure?

Cut-in is the pressure at which the pump starts running. Cut-out is the pressure at which the pump stops. The pump runs between these two points. For example, at 30 PSI cut-in and 50 PSI cut-out, the pump starts when pressure drops to 30 and stops when it reaches 50.

How do I know if my pressure switch is broken instead of just out of adjustment?

A broken switch usually will not respond to adjustment — the pump will either run constantly, never start, or cycle wildly no matter what you do. If you have adjusted both screws through their full range and the pump still does not behave normally, the switch itself may have failed and needs replacement. A professional can test it with a multimeter to confirm.

Can I adjust the pressure switch while the pump is running?

No. Always turn off power at the breaker and depressurize the tank before opening the switch. Adjusting under pressure risks water spray and injury. The pump can also start unexpectedly if you do not cut power at the breaker.

What pressure should I set my well pump to?

Most household systems work well between 30 and 50 PSI. If you want higher pressure for better shower flow, try 40 PSI cut-in and 60 PSI cut-out. If you want lower pressure to reduce wear on fixtures, try 20 PSI cut-in and 40 PSI cut-out. Avoid going below 20 or above 60 PSI without professional information.

Why does my pump keep cycling on and off every few minutes?

Rapid cycling usually means your pressure tank is waterlogged, you have a leak in the line, or the differential is set too small. Check the tank for water sloshing inside and inspect visible pipes for drips. If the tank is fine and you see no leaks, try increasing the differential by half a turn and test again.