Testing a pressure switch without tools or a plumber

A pressure switch tells your well pump when to turn on and off. When it stops working, your pump either runs constantly, won't start at all, or cycles too often. You can test whether the switch itself is the problem using a multimeter (a $15 to $30 electrical tester) and a few minutes at your pressure tank.

The test involves three steps: checking the air pressure in the tank, measuring electrical continuity across the switch terminals, and comparing what you find to the switch's rated settings. If the switch fails any of these, it needs replacement. If it passes, the problem lies elsewhere — in the pump, the tank, or the wiring.

Key Takeaways

  • A pressure switch controls when your pump runs; testing it requires a multimeter and knowledge of your tank's cut-in and cut-out pressures.
  • You must turn off power to the pump before opening the switch or testing its terminals to avoid electrical shock.
  • The switch should show electrical continuity (a complete circuit) when pressure is below the cut-in setting and no continuity when pressure is above the cut-out setting.
  • If the switch fails the continuity test, it has failed internally and must be replaced; if it passes, the problem is likely in the pump, tank, or wiring.
  • Most pressure switches cost $30 to $80 and take 15 minutes to swap out once you locate the correct model for your system.

Locate the pressure switch and find its settings

The pressure switch sits on top of or beside your pressure tank, usually mounted on a bracket or directly threaded into the tank. It looks like a small plastic or metal box with two or three wire terminals sticking out the bottom and a cover you can unscrew. Before you touch anything, turn off power to the pump at the breaker — this prevents accidental shock when you open the switch or test the terminals.

Next, find the switch's rated settings. Look for a label on the switch itself, on the tank, or in your well system's paperwork. The label will show two numbers: the cut-in pressure (when the pump turns on) and the cut-out pressure (when it turns off). A common setting is 30/50, meaning the pump starts at 30 pounds per square inch (psi) and stops at 50 psi. Your system may differ — check before you proceed.

Check the air pressure in the tank

Your pressure tank has an air valve on top that looks like a car tire valve. Use a tire pressure gauge to check the air pressure inside the tank. The reading should be about 2 psi below your cut-in pressure — so for a 30/50 system, aim for roughly 28 psi. If the tank pressure is much lower or zero, the tank's air bladder may have failed, which can cause the switch to behave erratically even if the switch itself is good.

If the tank pressure is very low, add air using a hand pump or compressor until you reach the target. If it drops again within a few days, the bladder is leaking and the tank will need replacement. Record the tank pressure — you will need it for the next test.

Test electrical continuity with a multimeter

A multimeter measures electrical current and continuity. Set the dial to the continuity or resistance setting (often marked with a sound-wave symbol or Ω). The multimeter will beep or show a reading near zero when two points are electrically connected, and show no beep or a high number when they are not.

Turn off power at the breaker. Unscrew the cover of the pressure switch to expose the terminals. You will see two or three metal posts. Consult your switch's wiring diagram (usually printed on the cover or available from the manufacturer) to identify which two terminals control the pump. Touch one multimeter probe to each of these terminals.

The switch should show continuity (a beep or near-zero reading) when the tank pressure is below the cut-in setting. If your tank is at 28 psi and your cut-in is 30 psi, the switch should beep. If it does not, the switch has failed internally. If the tank pressure is above the cut-out setting (say, 55 psi when cut-out is 50 psi), the switch should show no continuity. If it does show continuity, the switch has failed.

Interpret the test results

A working pressure switch shows continuity below cut-in and no continuity above cut-out. If your switch does this, it is functioning correctly and the problem lies elsewhere — in the pump motor, the capacitor, the wiring, or a tripped breaker. Check those components next or call a well service technician.

If the switch shows continuity when it should not, or fails to show continuity when it should, the internal contacts have stuck or corroded. The switch cannot be repaired and must be replaced. Write down the switch model number (printed on the cover) and order a replacement from a plumbing supply house or online retailer. Most switches cost $30 to $80 depending on the brand and pressure range.

Replacing the pressure switch

Once you have the replacement, turn off power at the breaker and drain the pressure tank by opening the drain valve at the bottom. Unscrew the old switch from the tank using an adjustable wrench — it threads in like a bolt. Wrap the threads of the new switch with plumber's thread seal tape (also called PTFE tape) and screw it in by hand, then tighten with the wrench until snug. Do not over-tighten, which can crack the plastic body.

Reconnect the wires to the same terminals they came from on the old switch. Restore power at the breaker. The pump should now cycle normally — turning on when pressure drops to cut-in and off when it reaches cut-out. If it still does not behave correctly, the pump or tank is the problem, not the switch.

When to call a technician instead

If you are uncomfortable working with electrical components or opening a pressurized tank, or if you do not have a multimeter, a well service technician can run this test for $75 to $150. They can also diagnose problems beyond the switch — a failing pump, a waterlogged tank, or a leak in the system — that you might not spot on your own.

If your tank pressure is very low and you cannot raise it, or if the pump runs constantly even after you replace the switch, stop and call a technician. These signs point to a tank or pump failure that requires professional equipment to diagnose safely.

Frequently Asked Questions

What does it mean if the pump runs all the time?

Constant running usually means the pressure switch is stuck in the "on" position, the tank air pressure is too low, or the pump is leaking water back into the tank. Test the switch first using the continuity method. If the switch passes, have a technician check the tank and pump.

Can I test the switch without a multimeter?

Not reliably. You can observe whether the pump turns on and off, but you cannot measure whether the switch's internal contacts are actually making or breaking the electrical connection. A multimeter is inexpensive and worth buying if you plan to troubleshoot your well system more than once.

What if the switch shows continuity at both high and low pressure?

The internal contacts are stuck closed. The switch has failed and must be replaced. This is the most common failure mode and means the switch cannot turn the pump off.

Do I need to drain the tank before replacing the switch?

Yes. The tank is pressurized, and opening the switch without draining first can spray water and cause injury. Always open the drain valve at the bottom of the tank and let the pressure drop to zero before unscrewing the switch.

How often do pressure switches fail?

Most switches last 5 to 10 years depending on water quality and how often the pump cycles. Hard water and frequent cycling shorten the lifespan. If your switch fails, replacing it is usually cheaper than repairing the pump.