What a pressure switch does and why you might adjust it
A pressure switch on your well pump turns the pump on when water pressure drops below a set point and turns it off when pressure reaches a higher set point. The difference between these two points is called the differential. If your pump is cycling too often, not building enough pressure, or running constantly, adjusting the switch may solve the problem — but only if the switch itself is the issue and not a leak, a waterlogged tank, or a failing pump.
Most residential well systems are set to a range of 30 to 50 pounds per square inch (psi), meaning the pump starts at 30 psi and stops at 50 psi. Some systems run 40 to 60 psi. Before you adjust anything, find out what your system is currently set to and what the manufacturer recommends for your pump and tank size. This information is usually on a label attached to the switch or in your pump documentation.
Adjusting the switch requires opening the cover, locating two adjustment screws, and turning them slightly. The work takes minutes, but getting the pressure right takes a few tries. You will need a pressure gauge to see what is actually happening inside the tank.
Key Takeaways
- A pressure switch has two adjustment screws: one controls the cut-in pressure (when the pump starts) and one controls the differential (the gap between start and stop).
- You must attach a pressure gauge to the system before adjusting anything, so you can see the actual pressure and know whether your changes are working.
- Turning the larger screw clockwise raises cut-in pressure; turning the smaller screw clockwise increases the differential and makes the pump run less often.
- Most adjustments are small — a quarter turn at a time — because even a few psi can change when the pump starts and stops.
- If the pump still cycles too fast or will not build pressure after adjustment, the problem is likely a leak, a waterlogged tank, or a failing pump, not the switch.
Gather a pressure gauge and locate the adjustment screws
You cannot adjust a pressure switch accurately without seeing what pressure the system actually has. Buy or borrow a water pressure gauge — they cost $10 to $30 at hardware stores and attach to any outdoor faucet or hose bib. Screw it on and turn on the faucet slightly. Write down the pressure reading when the pump is running and again after the pump shuts off. This tells you the current cut-in and cut-out pressures.
Next, locate the pressure switch itself. On most systems it is mounted on the pipe coming out of the pressure tank, usually near the tank or on the wall above it. The switch is a small box, often gray or black, with a cover held on by one or two bolts. Remove the cover carefully — do not force it. Inside you will see two adjustment screws, usually brass or steel. The larger screw (often labeled or marked with an arrow pointing up) controls the cut-in pressure. The smaller screw controls the differential.
Before you touch anything, take a photo of the current position of both screws. If something goes wrong, you can return them to where they started. Some switches have a small spring visible; do not disturb it.
Adjust the cut-in pressure if the pump starts too early or too late
The cut-in pressure is the point at which the pump turns on. If your pump is starting when the pressure is too low (say, 20 psi instead of 30 psi), you need to raise cut-in pressure. If it is starting too high (say, 40 psi when you want 30 psi), you need to lower it.
Use a flathead screwdriver that fits the larger adjustment screw snugly. Turn it clockwise (to the right) in quarter-turn increments to raise cut-in pressure, or counterclockwise (to the left) to lower it. After each quarter turn, wait 30 seconds and check your pressure gauge reading. The pump may take a moment to respond. Make one small adjustment, let the system settle, and read the gauge again before turning the screw further.
Stop when the pump starts at the pressure you want. For most homes, 30 psi is a good starting point. If you are unsure what your system should be, check the pump nameplate or call the pump manufacturer with your model number.
Adjust the differential if the pump cycles too often or not enough
The differential is the gap between cut-in and cut-out pressure. If your pump is turning on and off every few minutes (short cycling), the differential is too small. If the pump runs for a long time before shutting off, the differential may be too large.
The smaller adjustment screw controls differential. Turning it clockwise increases the differential — the pump will run longer before shutting off and will not restart as soon. Turning it counterclockwise decreases the differential — the pump will shut off sooner and restart sooner. Again, use quarter turns and check your gauge after each one.
A typical differential is 10 to 20 psi. If your pump is set to cut in at 30 psi, a 20 psi differential means it cuts out at 50 psi. This is a common setting for residential systems. If you increase the differential to 30 psi, the pump will not shut off until 60 psi, which may strain the tank and pump. If you decrease it to 5 psi, the pump will cycle very frequently, which wears it out faster.
Test the adjustment and watch for problems
After you adjust both screws, close the switch cover and turn on a faucet. Let the pump run until it shuts off, then watch the pressure gauge. The pump should start when pressure drops to your cut-in point and stop when it reaches your cut-out point. If the numbers are close to what you want, you are done. If they are still off, make another small adjustment, wait, and test again.
Run the system for a few hours and listen for short cycling — rapid on-and-off sounds. If the pump is still cycling every few minutes, the problem is not the switch. Check for leaks in the pressure tank, faucets, or supply lines. A leak will cause pressure to drop constantly, forcing the pump to restart. Also check whether the pressure tank is waterlogged — if it has no air cushion, it cannot store pressure and the pump will cycle constantly no matter what the switch is set to.
If the pump will not build pressure at all, even after adjustment, the pump itself may be failing. A worn pump cannot reach the pressure the switch is set for and will run continuously. This requires pump repair or replacement, not switch adjustment.
When to call a well service technician
If you are uncomfortable working with the switch, or if adjustment does not solve the problem, contact a well service company. They have the tools to measure pressure accurately, diagnose tank and pump problems, and replace the switch if it is faulty. A service call usually costs $100 to $300, depending on your location and what needs to be done.
You should also call a technician if the switch cover is stuck, if you cannot locate the adjustment screws, or if the pump behaves erratically even after adjustment. Some switches are not adjustable — they are sealed units designed for a single pressure range. If yours is sealed, it must be replaced, not adjusted.
Frequently Asked Questions
What pressure should my well pump be set to?
Most residential systems are set to 30 to 50 psi, with 30 psi cut-in and 50 psi cut-out being very common. Some systems run 40 to 60 psi. Check your pump documentation or the label on the switch for the manufacturer's recommendation. If you cannot find it, 30 to 50 psi is a safe starting point for most homes.
Can I adjust the pressure switch myself, or do I need a professional?
You can adjust it yourself if you are comfortable using a screwdriver and reading a pressure gauge. The work is straightforward and takes 15 to 30 minutes. If you are unsure about anything, or if adjustment does not fix the problem, hire a technician. A mistake will not damage the system, but it may not solve the issue.
Why is my pump cycling on and off every few minutes?
Short cycling usually means the differential is too small, but it can also mean the pressure tank is waterlogged, there is a leak in the system, or the pump is failing. Adjust the differential first — increase it by a quarter turn and test. If cycling continues, check for leaks and have the tank inspected. If the tank and lines are sound, the pump may need service.
What happens if I set the pressure too high?
Setting pressure above the tank's rated maximum can damage the tank and strain the pump. Most residential tanks are rated for 100 to 150 psi, so setting cut-out at 60 or 70 psi is safe. Do not exceed the tank's rating, which is stamped on the tank itself. If you are unsure, keep cut-out below 60 psi.
Do I need to turn off power to the pump before adjusting the switch?
It is safer to turn off power at the breaker before opening the switch cover, so the pump cannot start unexpectedly while you are working. You do not need to drain the tank. Once you close the cover and restore power, the system will operate normally.