Wire your well pump by running cable from the breaker box through conduit to the pump, connecting the hot, neutral, and ground wires to the correct terminals, and setting the breaker to match the pump's amperage
Well pump wiring is not complicated, but it must be done correctly — a loose connection or wrong wire gauge will either stop the pump from running or create a fire hazard. The job involves running electrical cable from your home's breaker box to the pump location, protecting that cable in conduit, and connecting three wires (hot, neutral, and ground) to the pump's terminal box. Most residential well pumps run on 240 volts and draw between 15 and 50 amps, depending on the pump's horsepower.
This guide covers the wiring itself, not the plumbing or the pump installation. You will need to know your pump's voltage, horsepower, and full-load amperage (FLA) — all printed on the pump's nameplate. If you are not comfortable working inside a breaker box or running conduit, hire a licensed electrician; the cost is usually $300 to $800 and is worth the safety margin.
Key Takeaways
- Well pump wire gauge and breaker size must match the pump's full-load amperage, not just its horsepower.
- Cable must run through rigid or flexible conduit from the breaker box to the pump to protect it from damage and meet code.
- The hot wire connects to the breaker, the neutral to the neutral bus, and the ground to the ground bus in the breaker box.
- At the pump, the hot and neutral wires connect to the pump's motor terminals, and the ground wire bonds to the pump's metal frame or ground lug.
- Most jurisdictions require a permit and inspection before the pump can be energized, even if you do the work yourself.
Determine wire gauge and breaker size from the pump nameplate
The pump's nameplate lists its full-load amperage (FLA), which is the number you use to size the wire and breaker — not the horsepower. A 1.5 horsepower pump might draw 12 amps, while a 2 horsepower pump might draw 15 amps; the actual draw depends on the pump's design and efficiency. Look for a metal or plastic label on the pump motor itself, usually near the terminal box.
Once you have the FLA, use the National Electrical Code (NEC) Table 310 to find the correct wire gauge. For a 15-amp pump, you need 14 AWG wire. For 20 amps, use 12 AWG. For 30 amps, use 10 AWG. For 40 amps, use 8 AWG. The breaker size should match the wire gauge: a 15-amp breaker with 14 AWG wire, a 20-amp breaker with 12 AWG wire, and so on. Using undersized wire with an oversized breaker will let the wire overheat before the breaker trips.
If the pump is more than 100 feet from the breaker box, go up one wire size. A 15-amp pump at 150 feet needs 12 AWG instead of 14 AWG. This accounts for voltage drop over the longer run.
Run conduit from the breaker box to the pump location
Electrical code requires the cable to be protected in conduit for its entire run from the breaker box to the pump. Use rigid metal conduit (RMC), intermediate metal conduit (IMC), or Schedule 40 PVC conduit. PVC is cheaper and easier to work with, but it cannot be used indoors or in areas where it might be damaged. Rigid metal conduit is stronger and required in some jurisdictions.
The conduit diameter depends on the wire gauge. For 14 or 12 AWG wire, use 1/2-inch conduit. For 10 AWG, use 3/4-inch. For 8 AWG, use 1-inch. Run the conduit from a knockout hole in the breaker box, through walls or along the exterior of the house, and down to the pump's terminal box. find the conduit every 3 feet with straps or clamps. At the breaker box and pump, use a conduit connector to attach the conduit and seal the opening.
If the pump is in a well pit or below ground, the conduit must extend at least 18 inches above the finished grade to keep water out. Seal the top of the conduit with a weatherproof cap or connector to prevent rain from entering.
Pull wire through the conduit and connect at the breaker box
Use individual THHN or THWN wires (single-conductor, rated for wet locations) rather than NM cable (Romex), which is not allowed in conduit. You need three wires: one hot (black), one neutral (white), and one ground (bare copper or green). All three must be the same gauge as determined from the pump's FLA.
Pull the wires through the conduit from the breaker box end. Use a fish tape if the run is long or has bends. Leave 6 inches of wire sticking out at both ends for connections. At the breaker box, turn off the main breaker and lock out the box if possible. Remove the cover and locate an open breaker slot. Install a new breaker of the correct amperage (matching your wire gauge) in that slot.
Connect the black (hot) wire to the breaker's terminal screw. Connect the white (neutral) wire to the neutral bus bar — a long metal bar with multiple screw terminals, usually on the left side of the box. Connect the bare copper or green (ground) wire to the ground bus bar, which is usually next to or part of the neutral bus. Tighten all three screws firmly. Replace the breaker box cover and restore power to the main breaker.
Connect wires to the pump's terminal box
At the pump end, the three wires enter the pump's terminal box through a conduit connector. Inside the box are three terminals: two for the motor windings (hot and neutral) and one for ground. The terminals are usually labeled H (hot), N (neutral), and G (ground), or they may be numbered 1, 2, and 3.
Strip 3/4 inch of insulation from each wire. Connect the black (hot) wire to the H or terminal 1. Connect the white (neutral) wire to the N or terminal 2. Connect the bare copper or green (ground) wire to the G terminal or to a ground lug bolted to the pump's metal frame. Use a wire connector (crimp terminal or screw terminal) rated for the wire gauge. Tighten the terminal screws firmly — a loose connection will cause the pump to overheat or fail to start.
If the pump has a pressure switch or control box, the wires may connect there first, then branch to the pump motor. Follow the wiring diagram that came with the pump or switch. Do not assume the terminals are in the same order as another pump's.
Test the circuit and have it inspected
Before turning on the pump, check your work. Verify that the breaker is off. Use a multimeter set to AC voltage to confirm there is no power at the pump terminals. Check that all wire connections are tight and that no bare copper is exposed. Inspect the conduit for damage or gaps.
Turn the breaker on and listen for the pump to start. If it does not, turn the breaker off when ready and check the connections. If the breaker trips as soon as you turn it on, there is a short circuit — turn it off and do not try again until you find the problem.
Most jurisdictions require a permit and inspection before a well pump can be energized. Contact your local building department or electrical inspector to request an inspection. They will check the wire gauge, breaker size, conduit routing, and terminal connections. If everything passes, they will issue a permit or sign-off. Do not skip this step — an unpermitted installation can void your homeowner's insurance and create a liability if someone is injured.
Common wiring mistakes to avoid
Using undersized wire is the most common mistake. A 20-amp pump wired with 14 AWG wire will overheat the insulation and eventually fail or catch fire. Always match the wire gauge to the pump's FLA and the breaker size to the wire gauge.
Connecting the neutral and ground wires to the same terminal at the pump is another error. The neutral carries current back to the breaker box; the ground is a safety path only. If they share a terminal, a fault in the pump can energize the metal frame, creating a shock hazard. Keep them separate at the pump.
Running cable without conduit saves time but violates code and leaves the wire exposed to damage from tools, rodents, or weather. Conduit is cheap insurance. Failing to get a permit or inspection is tempting but risky — the inspector catches mistakes before they cause a problem, and the permit protects you legally if something goes wrong later.
Frequently Asked Questions
Can I use regular household wire (Romex) instead of individual THHN wires in conduit?
No. Romex is not rated for wet locations and is not allowed in conduit. Use individual THHN or THWN wires, which are designed for wet environments and can be pulled through conduit without damage.
What if my pump is 200 feet from the breaker box?
Go up two wire sizes to account for voltage drop. A 15-amp pump at 200 feet needs 10 AWG wire instead of 14 AWG. Voltage drop becomes significant at long distances and will reduce the pump's starting torque and efficiency.
Do I need a disconnect switch between the breaker and the pump?
Code typically requires a disconnect switch within sight of the pump so you can shut off power without going back to the breaker box. A straightforward 240-volt disconnect switch costs $30 to $60 and takes 10 minutes to install in the conduit run near the pump.
What happens if I connect the hot and neutral wires backward at the pump?
The pump will still run, but the motor will spin in the wrong direction. This can damage the pump or cause it to fail to prime. Check the pump's wiring diagram to confirm which terminal is hot and which is neutral, then verify your connections before energizing.
Can I bury the conduit underground instead of running it above ground?
Yes, but it must be buried at least 18 inches deep and protected with Schedule 40 PVC or rigid metal conduit. Direct burial cable (marked UF) can be buried without conduit, but it is more expensive and still requires 18 inches of depth. Check your local code — some jurisdictions have different depth requirements.