What a pressure switch does and why it matters

A pressure switch is a small electrical device that turns your well pump on and off based on water pressure in your tank. When pressure drops below a set point, the switch closes an electrical circuit and the pump runs. When pressure rises to the upper set point, the switch opens the circuit and the pump stops. If your switch is set wrong, your pump will cycle too often, run constantly, or fail to deliver water when you turn on a faucet.

The two numbers you need to know are the cut-in pressure (when the pump starts) and the cut-out pressure (when it stops). Most residential well systems are set to cut in at 30 psi and cut out at 50 psi, but your tank's size, your water use, and your plumbing code may call for different settings. Adjusting these settings yourself is possible, but it requires a pressure gauge, an understanding of how your specific switch works, and caution around electrical connections.

Key Takeaways

  • A pressure switch controls when your pump turns on and off by measuring water pressure in your tank.
  • Most residential systems use a 30/50 psi setting (pump starts at 30, stops at 50), but your system may differ based on tank size and local code.
  • You will need a reliable pressure gauge, an adjustable wrench or screwdriver, and a way to safely cut power to the pump before opening the switch.
  • Adjusting the switch involves loosening a nut, turning adjustment screws, and testing with the gauge until pressure readings match your target.
  • If the switch is damaged, leaking, or you are unsure about electrical safety, call a licensed well contractor rather than attempt repair.

Gather the tools and information you need

Before you touch the switch, collect what you will need. A 0–100 psi pressure gauge is essential—do not guess at pressure by feel or sound. You can buy one at any hardware store for $15 to $40, or borrow one if you know someone with a well. You will also need an adjustable wrench or the correct screwdriver size for your switch model (usually a flathead or Phillips). Check your switch's label or manual to see which adjustment screws control cut-in and cut-out pressure; they are often labeled or color-coded.

Find out what pressure settings your system should have. Look at your pressure tank's nameplate or check your well contractor's paperwork if you have it. If you have no record, 30/50 psi is a safe starting point for most homes, but verify this does not conflict with your local plumbing code—some areas require different settings. Write down the target numbers before you start so you do not have to guess mid-adjustment.

Turn off power and depressurize the system

Locate the electrical disconnect switch or breaker that controls your well pump. This is usually a switch on the pump itself, on the pressure tank, or on your home's electrical panel. Turn it off and lock it or tag it so no one turns it back on while you are working. Do not skip this step—working on a live electrical circuit can cause serious injury.

Next, open a faucet or outdoor spigot to release pressure from the tank. Let water run until it stops flowing, which means the tank is empty and depressurized. This protects you from a sudden spray of water when you open the switch cover. Once the tank is empty and power is off, you are ready to access the switch.

Locate the pressure gauge port and test current pressure

Your pressure tank has a small port (usually a 1/4-inch fitting) where you can screw on a pressure gauge. This port is often on top of the tank or on the side near the pressure switch. Screw your gauge onto this port by hand—do not use a wrench unless it is very tight. Once the gauge is on, turn the electrical power back on and let the pump run until it stops. The pressure reading when the pump shuts off is your current cut-out pressure.

Turn on a faucet to lower the pressure and watch the gauge. When the pump kicks back on, that reading is your current cut-in pressure. Write both numbers down. If they are already where you want them, you do not need to adjust anything. If they are off, turn the power back off, depressurize again, and move to the next step.

Open the switch and identify the adjustment screws

The pressure switch is a small box bolted to or near the pressure tank. It has a cover held on by one or more bolts or screws. Remove these fasteners and carefully lift off the cover. Inside you will see two adjustment screws or nuts, usually labeled or color-coded. One controls cut-in pressure (often labeled with a minus sign or "–"), and one controls cut-out pressure (often labeled with a plus sign or "+"). Some switches have a single nut that adjusts the range between cut-in and cut-out instead.

Consult your switch's manual or the label on the cover to confirm which screw does what. If you cannot find the manual, take a photo of the label and search online for your switch model number. Turning a screw clockwise usually increases pressure, and counterclockwise decreases it, but this varies by design. Do not assume—verify before you turn anything.

Adjust the screws and test with the gauge

Make small adjustments: turn each screw only one-quarter turn at a time. After each adjustment, screw the gauge back onto the tank port, turn power on, and run the pump through a full cycle. Watch the gauge to see where the pump now starts and stops. Write down the new readings. Turn power off, depressurize, and make another quarter-turn if needed. This slow process takes longer but prevents overshooting your target pressure.

If you need to raise cut-in pressure, turn the cut-in adjustment screw clockwise. If you need to lower it, turn counterclockwise. Do the same for cut-out pressure using the cut-out screw. Once both readings match your target (for example, 30 psi cut-in and 50 psi cut-out), stop adjusting. Screw the cover back on, remove the gauge, and run the system normally for a few days to make sure the settings hold steady.

When to call a professional instead

Do not attempt this adjustment if the switch is visibly cracked, leaking water, or corroded. A damaged switch cannot be safely adjusted and must be replaced by a licensed well contractor. If you are uncomfortable working with electrical connections, or if you adjusted the screws but the pressure readings do not change, stop and call for help. Forcing a stuck screw or guessing at electrical safety can damage the switch or create a hazard.

Also call a professional if your pump cycles on and off constantly even after adjustment, or if it will not start at all. These symptoms often point to a failed pressure tank bladder, a broken check valve, or a pump problem—not a switch adjustment. A contractor can diagnose the real issue and fix it correctly.

Frequently Asked Questions

What happens if I set the pressure too high?

High pressure puts extra stress on your pipes, fittings, and appliances, and can cause leaks or burst pipes over time. It also makes your pump work harder and wear out faster. If you set cut-out pressure above 60 psi, you are likely too high for a residential system. Check your local code or call your contractor to confirm the safe upper limit for your setup.

Can I adjust the switch without turning off power?

No. The switch contains live electrical contacts that can shock you, and opening it while power is on is dangerous. Always turn off power at the breaker or disconnect switch and lock it before you open the switch cover. This is not optional.

Why does my pump keep running even after I adjusted the switch?

A pump that will not stop usually means the switch adjustment did not take, or the switch itself is faulty. It can also mean your pressure tank's bladder has failed and no longer holds pressure. Turn off the pump, depressurize the tank, and check your gauge readings again. If they are not where you set them, the switch may be stuck or broken and needs replacement by a contractor.

How often should I check or adjust the pressure switch?

Most well systems need adjustment only once every few years, unless you notice a change in water pressure or your pump behavior shifts. If your pump starts cycling more often or your water pressure drops, check the gauge and compare it to your target settings. Seasonal temperature changes can shift pressure slightly, but large changes usually signal a problem worth investigating.

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

Cut-in is the pressure at which the pump turns on; cut-out is the pressure at which it turns off. The difference between them (called the differential or range) is usually 20 psi on residential systems. A 30/50 setting means the pump starts at 30 psi and stops at 50 psi. A wider range (like 20/40) means the pump runs less often but delivers less water between cycles.