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This guide follows the official manufacturer procedure
The diagnostic steps and corrective actions below are based on Schneider Electric's Data Bulletin 9013DB0701, "Preventive Maintenance and Troubleshooting Guidelines for Class 9013F and 9013G Pressure Switches" — the Square D Pumptrol line that's the de facto standard in residential well systems. If your switch is a different brand, the same diagnostic logic almost always applies, since most residential pressure switches use the same diaphragm/contact design.
Before you touch the switch — 4 checks every time
Confirm power is reaching the switch
Check the circuit breaker and any disconnect switch at the wellhead. Check line voltage with the pump on and off.
Record the current pressure switch setting
Note the existing cut-in and cut-out readings before you change anything, so you have a baseline to return to if needed.
Visually inspect for leakage
With power disconnected, remove the cover and check for liquid leaking from the diaphragm or flange area, corrosion at the flange, or standing water/wet spots nearby.
Check plumbing and electrical connections
Verify fittings are secure with no white lime residue, and wires aren't pinched, frayed, or have cracked insulation. Check for insect nests inside the housing — this is a more common cause of failure than most people expect.
Important: never clean contacts with sandpaper, files, or chemicals
Per the manufacturer's bulletin: contacts may appear pitted from normal use. Do not sand or file the contacts, and do not use chemicals to clean them — this damages the contact surface and accelerates failure rather than fixing the problem.
No water flow
Cause: power is off
Confirm power is actually reaching the switch before doing anything else.
Cause: low or marginal well (low pressure cutout switches)
Check the pressure tank reading. If pressure is below cut-in and your switch has a low pressure cutout feature (Form M4), hold the lever in Run position — the pump should turn on. If releasing the lever cuts the pump out again within 10 PSI of cut-in, the water source itself is low. Don't re-actuate the lever until the well has had time to recharge.
If your switch doesn't have Form M4: turn off power to the pump until the source has recharged. Running a pump against a dry or near-dry well damages the motor.
Cause: the line to the switch is plugged, so it can't read tank pressure
If tank pressure is actually below the cut-in setting but the switch isn't responding, the sensing line may be obstructed and reading false pressure.
Procedure for qualified personnel: Remove the switch from the pipe and confirm the diaphragm entry is free of silt and debris. Confirm any check valves between the well and pressure tank are functioning. Confirm the pressure reading at the switch actually matches the tank.
Rapid cycling (erratic operation)
Waterlogged tank — check the bladder first
Manufacturer's test procedure: Drain some air from the tank's compressed air valve stem. If water comes out instead of air, the bladder has failed. Completely drain the bladder and recharge with air per the correct specification.
If the tank is below cut-in pressure when you check it, the bladder or air valve likely has a leak that needs addressing before the pressure switch will behave normally.
Cause: undersized tank
If the bladder checks out fine, the tank itself may simply be too small for household demand. Restrict water usage (limit simultaneous fixture use) as a temporary fix, or install a larger tank as the permanent solution.
Cause: major leak in service lines
Visible water or wet spots, combined with the pump running but the tank filling slowly, points to a leak. Check for and repair any damaged pipes.
Cause: faulty check valve (open)
An open or leaking check valve lets water flow back into the well, emptying the tank between uses. Check for a leaking valve and replace if defective.
Cause: foreign material / calcium deposits blocking the sensing line
Lime buildup can block the line to the switch so it perceives constant high pressure. If tank pressure is below cut-in but the switch isn't responding correctly, this is likely the cause — clean or replace the affected line.
Cause: no holding tank installed
If there's no pressure tank at all in the system, install a properly sized one — this is a design issue, not a switch failure.
Pressure switch chattering (contact chatter or bounce)
Cause: incorrect air pressure in the bladder
Adjust to manufacturer's specification using the waterlogged tank procedure above. For conventional (non-bladder) tanks, check the air volume control, drain and recharge as needed.
Cause: excessive vibration
A switch mounted on rigid pipe with brackets secured to the structure, combined with a tightly secured pump, can amplify vibration into the switch mechanism. Mount the switch to a less rigid section of pipe and shock-mount any brackets to isolate it from the vibration source.
Long pump run, or pump will not shut off
Too many water outlets running
Limit the number of fixtures running at any one time, or if this is a recurring demand issue, increase the size of the pump and/or storage tank.
Worn pump parts
For qualified service personnel: Check the pump for worn impellers, casing, or other close-fitting parts that have degraded and reduced output despite the motor running normally.
Water leaks or plugged discharge pipes
Check service lines for leaks and repair. Check for plugged discharge pipes causing reduced flow that makes the system think it hasn't reached pressure — replace damaged pipe or clear the obstruction.
Pump shuts off immediately after startup (related issue)
High-pressure pumps or new pump installs can trip the switch immediately on startup due to pressure surge. The manufacturer's fix is a surge reducer fitting at the switch.
Switch contacts severely burned
Insects or debris between the contacts
Remove nests or other insect havens near the switch, then replace the burned contacts (a contact kit, not the full switch, is often sufficient).
Pump is too large for the switch's rating
If the motor load exceeds the switch's electrical rating, add a contactor designed for that load rather than wiring the pump directly through the switch.
Application requires heavy-duty contacts
For high-cycle or high-load applications, replace with a switch rated for heavy-duty contacts and higher horsepower.
Welded (overloaded) contacts
If contacts are fused together from overload, the switch is no longer functional and the entire unit needs replacement — a contact kit won't fix welded contacts.
Switch will not trip at desired pressure
Incorrect pressure settings
Adjust to the correct setting using the procedure in the "How to adjust" section below.
Defective pressure gauge
Test the gauge itself before assuming the switch has failed — a bad gauge reading makes a properly functioning switch appear faulty. Replace the gauge if it tests bad.
Damaged diaphragm actuator
If settings and gauge both check out, the diaphragm itself needs replacement.
Cannot adjust to desired pressure
If the desired setting falls outside the switch's rated range and differential limits, no amount of adjustment will get there — replace the switch with one rated for your target range.
Switch operates mechanically but not electrically
No power to the switch
Apply power and check the circuit breaker or disconnect switch. On new installations, also verify the wiring itself before resetting the breaker repeatedly.
Damaged or improperly installed wiring
Confirm the switch is wired to the correct contact terminals. Make new connections or tighten existing ones if corroded or loose.
Damaged or overloaded (welded) contacts
Replace the contacts or the entire switch. As with the no-flow scenario above, also check that the diaphragm entry is free of silt, check valves are functioning, and the pressure reading at the switch is accurate.
How to adjust the pressure switch — official procedure
Two adjustment nuts control different things. Understanding the difference prevents you from chasing the wrong setting.
Tool needed: 3/8 inch nut driver or socket.
Official renewal part chart from Schneider Electric. These are approximate turn counts for common setting changes — always verify against your gauge as you adjust.
Set bladder tank air pressure first
If changing the cut-in setting, the bladder needs to be set 2 PSI below the new cut-in pressure. Turn off power, drain water from the tank, check the air reading, and add/remove air via the valve to reach the correct pressure before adjusting the switch itself.
To change cut-in (and shift cut-out equally): turn the range nut
Clockwise raises cut-in; counterclockwise lowers it. The differential stays fixed, so cut-out moves by the same amount.
To change cut-out only (cut-in stays the same): turn the differential nut
Clockwise raises cut-out; counterclockwise lowers it.
Verify by opening a faucet
Open a faucet and drain water until the pump turns on (confirms cut-in), then close it and watch the gauge for where the pump shuts off (confirms cut-out). Repeat adjustments as needed until both readings match your target.
Routine maintenance checklist (manufacturer recommended)
Performing this checklist annually catches most failures before they leave you without water.
- Disconnect power
- Remove the cover
- Visually inspect for leakage at the diaphragm or flange, corrosion, and standing water nearby
- Check all plumbing connections for corrosion and lime residue
- Check all electrical connections for pinched/frayed wires, cracked insulation, and insect contamination
- Check system pressure with a gauge
- Replace the cover
- Restore power and confirm pump operation
- Open a tap to confirm water flow
If it's time to replace — the Square D FSG2
Square D 9013 FSG2 Pressure Switch (30/50 PSI)
The Pumptrol design by Schneider Electric is the de facto residential standard — metal housing, brass contacts, diaphragm actuator, IP54 rated for dust and splash protection. Compatible with jet, submersible, and reciprocating pumps. Standard 30/50 PSI factory setting, field-adjustable to other ranges using the procedure above.
Installation note: Verify NPT thread type and connector orientation before swapping — some installations require reusing a small fitting from the old switch for a perfect fit. Quick-disconnect terminals make the wiring straightforward once mounted.
Not smart-home compatible — this is a mechanical/electrical switch, not a connected device.
Check Price on Amazon →Common questions
What's the difference between the range nut and the differential nut?
The range nut adjusts cut-in pressure — the differential stays fixed, so cut-out shifts by the same amount in the same direction. Raise cut-in 10 PSI, cut-out also rises 10 PSI. The differential nut adjusts only cut-out; cut-in stays exactly where it was. Both use a 3/8 inch nut driver.
Why does my pressure switch chatter or buzz?
Most commonly incorrect bladder air pressure — fix using the waterlogged tank procedure. If that's not it, excessive vibration from rigid pipe mounting near a tightly secured pump is the next most likely cause. Mount the switch to a less rigid section and shock-mount any brackets.
Can I use a water pump switch on an air compressor?
Per Schneider Electric, generally yes for compatible forms, but a 9013FSG water pump switch specifically cannot be used on a compressor requiring Form X. Verify the specific form code before substituting between applications.
How do I know if my pressure switch contacts are actually bad?
Pitting from normal arcing is expected and doesn't mean failure — never sand, file, or chemically clean the contacts. Severely burned contacts point to an undersized switch for the pump load, insects/debris, or an application needing heavy-duty contacts. Welded (fused) contacts mean the switch needs full replacement.