Well pumps · how-to
Replacing a 40/60 well pressure switch
The pressure switch is the small gray box near your pressure tank that turns the well pump on and off. When it fails, the house loses water or the pump will not shut off. Here is how to recognize a bad switch, match the replacement, and what a safe swap looks like — and when to hand it to a pro.
Symptoms of a failing pressure switch
- No water, pump not running, and tapping the switch cover makes it click on — burned or pitted contacts.
- Chattering or buzzing at the switch as pressure nears cut-in or cut-out.
- Pump will not shut off even when the gauge is at or above the cut-out setting.
- Erratic cut-in/cut-out — often a clogged sensing port or nipple underneath the switch, not just the switch itself.
- Visible scorching, melted plastic, ants or insects inside the cover.
Rapid on/off cycling is usually not the switch — it is more often a waterlogged tank or wrong precharge. Check the tank before replacing parts — see pressure tank precharge. Low pressure overall can also be a pump, well yield, or plumbing issue; see residential well pump basics.
Matching the replacement
- Pressure range: “40/60” means the pump turns on at 40 psi and off at 60 psi. Replace like-for-like (30/50 and 40/60 are the common residential settings) unless a pro has a reason to change it.
- Electrical rating: confirm the switch is rated for your pump’s voltage and horsepower. The Square D 9013FSG2J24 is a common 40/60 residential switch rated up to 1½ HP at 120 V and 2 HP at 240 V per its listing.
- Low-pressure cutoff: some switches add a lever that shuts the pump off if pressure collapses (for example, a broken pipe or a dry well). If yours has one, replace it with a cutoff model.
- Connection: most mount on a ¼″ female threaded port. Plan to replace the small nipple under the switch at the same time — they often clog with sediment or corrode.
What a safe swap looks like
- Power off at the pump breaker. Verify dead at the switch terminals with a tester.
- Relieve pressure: open a nearby faucet or the tank tee drain until the gauge reads zero.
- Photograph the wiring — line (from the breaker) vs load (to the pump) and the ground.
- Disconnect wires, unscrew the old switch, and inspect the nipple and tank-tee port. Clear or replace anything clogged.
- Seal the threads per the manufacturer’s instructions and thread the new switch on. Do not overtighten by twisting the switch body against its base.
- Rewire exactly as before, including the ground. Close the cover.
- Check tank precharge with the system at zero water pressure. A common rule is about 2 psi below cut-in (around 38 psi for a 40/60 switch) — follow your tank maker’s instructions.
- Restore power and watch the gauge through a full cycle: the pump should start near cut-in and stop near cut-out.
Adjusting the settings (only if needed)
On common Square D-style switches, the large spring nut moves cut-in and cut-out together, and the small spring nut changes the cut-out (the differential). Make small adjustments with power off, then retest. Never set cut-out above what your tank, pump, and plumbing are rated for, and keep precharge matched to the new cut-in. If you are chasing more pressure, the pump and well may be the real limit — see sizing by GPM and total head.
Pressure switch vs constant pressure
A pressure switch gives a pressure swing between cut-in and cut-out. Grundfos SQE systems with a CU 301-class controller use a pressure sensor and variable speed to hold steadier house pressure instead. If you are replacing switches repeatedly or the pump is near end of life, compare the options in SQ vs SQE (constant pressure / CU).
When to call a pro
- The switch is fine but the pump still will not start — that points to the control box, wiring, or the pump itself.
- Burned wiring, aluminum wire, or a breaker that trips when the pump starts.
- The pump runs but cannot reach cut-out pressure.
- Anything involving pulling the pump or work inside the well.
For electrical work and well service, use a licensed electrician or licensed well contractor. If the pump itself needs replacing, R.E. Merrill & Associates is a Grundfos dealer — we can talk through SQ and SQE options with you and your contractor. Contact R.E. Merrill & Associates.
Hard-water cross-links
- Iron in well water — sediment and iron are a common reason switch nipples clog
- Best water hardness test kits — test well water before choosing treatment
Sources
- Schneider Electric / Square D 9013FSG2J24 product datasheet and listing — 40/60 psi setting, 15–30 psi adjustable differential, ¼″ female port, 1½ HP @ 120 V / 2 HP @ 240 V.
- Pressure tank manufacturer guidance — set precharge with water pressure at zero, commonly about 2 psi below cut-in.