What a pressure switch does and why you adjust it
A pressure switch is a small electrical device mounted on the pressure tank that tells your well pump when to turn on and off. It monitors the water pressure inside the 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.
You adjust a pressure switch when your pump is cycling too often (short-cycling), not building enough pressure, or when you want to change the pressure range to match your household needs. A well-functioning switch prevents the pump from running constantly and protects the tank and plumbing from pressure swings.
Before you touch anything: turn off power to the pump at the breaker. Pressure switches have live electrical contacts, and the tank holds pressurized water. Work safely by de-energizing the system first.
Key Takeaways
- A pressure switch has two adjustment screws — one for the cut-in pressure (when the pump starts) and one for the differential (the gap between start and stop).
- Most household wells are set to cut in around 30 to 40 psi and cut out around 50 to 60 psi, but your system's correct range depends on your tank size and plumbing layout.
- Turn off the breaker before opening the switch cover, and use a pressure gauge on the tank to read the current settings before making any changes.
- Turning the larger screw clockwise raises the cut-in pressure; turning the smaller screw clockwise raises the differential.
- After adjustment, monitor the pump for a full day to confirm it cycles normally and pressure stays within your target range.
Locate the pressure switch and read the current settings
The pressure switch is a small cylindrical or rectangular housing bolted to the top or side of your pressure tank, usually near where the pump line enters. It has a cover held on by one or two bolts. Before you open it, attach a pressure gauge to the test port on the tank — this is a small valve that looks like a tire valve stem, usually found on the tank's side or top.
Record the pressure reading with the pump running and the pressure reading after the pump shuts off. The first number is your cut-out pressure (pump stops here); the second is your cut-in pressure (pump starts here). The difference between them is the differential. For example, if the pump stops at 60 psi and starts at 40 psi, your differential is 20 psi.
Write these numbers down. You will need them to know whether adjustment is necessary and to confirm your changes worked.
Understand the two adjustment screws
Inside the switch cover are two adjustment screws, usually labeled or color-coded. The larger screw (often with a spring underneath) controls the cut-in pressure — the point at which the pump starts. The smaller screw controls the differential — how far the pressure must drop before the pump starts again.
Turning the large screw clockwise raises the cut-in pressure; counterclockwise lowers it. Turning the small screw clockwise increases the differential (makes the pump wait longer before starting); counterclockwise decreases it. Each full turn typically changes pressure by 2 to 5 psi, depending on the switch model.
Some switches have the screws arranged differently — check your switch's label or the pump manual to confirm which screw does what before you turn anything. Turning the wrong screw will not damage anything, but it will waste your time.
Make small adjustments and test
Start with the large screw if you need to raise the overall pressure range, or the small screw if you only need to change how often the pump cycles. Turn the screw one-quarter turn, then turn the breaker back on and let the pump run through one full cycle — from start to stop. Watch the pressure gauge and note the new cut-in and cut-out readings.
If the change is in the right direction but not enough, turn off the breaker again and adjust another quarter turn. If the change went the wrong way, you turned the wrong screw — turn it back and try the other one. Make one adjustment at a time and test between each one. This takes longer but prevents overshooting.
Typical household settings are 30 to 40 psi cut-in and 50 to 60 psi cut-out, but the right range for your home depends on your tank volume, the number of fixtures, and how much pressure drop you can tolerate between pump cycles. If you are unsure what your target should be, consult your pump manual or call a well service technician — they can recommend settings based on your system.
Watch for short-cycling and tank problems
If the pump turns on and off every few seconds, the tank's air charge may be low, not the switch setting. A pressure tank contains both water and compressed air; the air acts as a cushion. When the air charge leaks out, the pump cycles constantly even with correct switch settings. Check the air charge by turning off the breaker, draining the tank completely, and using an air compressor to refill it to about 2 psi below your cut-in pressure.
If short-cycling continues after you recharge the air, then adjust the switch. If you raise the cut-in pressure and the pump still cycles too often, the tank air is the real problem, not the switch. Replacing the air charge is cheaper and faster than chasing switch adjustments that will not fix the underlying issue.
When to call a professional instead
If the pressure gauge does not move when the pump runs, or if pressure drops to zero when the pump stops, the switch itself may be faulty or the tank may have a leak. Do not keep adjusting — call a well service technician. A broken switch will not respond to adjustment, and a leaking tank will lose pressure no matter what the switch is set to.
If you are not comfortable working with pressurized systems or live electrical contacts, or if your pump is still under warranty, have a technician do the adjustment. The cost is usually $100 to $200 and takes less than an hour. It is worth paying to avoid damaging the switch or injuring yourself.
Frequently Asked Questions
How much should I turn the adjustment screw?
Start with one-quarter turn, then test the pump through a full cycle. Each quarter turn typically changes pressure by 0.5 to 1.5 psi. Make small adjustments and test between each one rather than turning the screw multiple times before checking results.
What is the normal pressure range for a home well pump?
Most household systems run between 30 to 40 psi cut-in and 50 to 60 psi cut-out, but the correct range depends on your tank size, plumbing layout, and how many fixtures you have. Your pump manual or a well service technician can recommend the best setting for your specific system.
Can I adjust the switch while the pump is running?
No. Always turn off the breaker first. The switch contains live electrical contacts, and the tank is pressurized. Working on a live system risks electrical shock and sudden pressure release. Turn the breaker off, make your adjustment, then turn it back on to test.
Why does my pump keep turning on and off every few seconds?
Short-cycling is usually caused by a low air charge in the pressure tank, not a faulty switch. Drain the tank completely and refill the air charge to about 2 psi below your cut-in pressure using an air compressor. If cycling continues after recharging the air, then adjust the switch settings.
Do I need to drain the tank before adjusting the switch?
No. The switch adjustment does not require draining. You only need to turn off the breaker and attach a pressure gauge to monitor the current and new settings. Draining is only necessary if you need to recharge the tank's air cushion.