The well pump breaker trips. You reset it. It runs for a while and trips again. Or it trips immediately. You call a well service company and they quote $2,500 to pull the pump and replace it. Before you write that check, understand that the pump itself is only one of five possible causes, and it is not even the most common one. Pulling a pump from a 200-foot well is expensive, time-consuming, and completely unnecessary if the problem is a bad pressure switch, a failed capacitor, a waterlogged pressure tank, or voltage drop on the feed wire.
This guide walks through the five most likely causes of well pump breaker trips in order of probability and cost to diagnose. By working through them systematically, you can often identify the problem with a multimeter and a pressure gauge before committing to a pump pull. Even if the pump does need replacement, understanding the root cause prevents you from installing a new pump into the same conditions that killed the old one.
Cause #1: Pressure Switch Sticking or Burnt Contacts
The pressure switch is a $15 to $30 device mounted on the plumbing near the pressure tank. It turns the pump on when pressure drops to the cut-in setting (typically 30 or 40 PSI) and off when pressure reaches the cut-out setting (typically 50 or 60 PSI). When the contacts inside the switch burn, pit, or weld together, the switch can cause the pump to run continuously, cycle rapidly, or fail to shut off when pressure is reached. Any of these conditions can trip the breaker.
Burnt contacts are the most common pressure switch failure. Every time the switch opens or closes under load, a tiny arc forms across the contacts. Over time, this arc erodes the contact surfaces, increasing resistance. Higher resistance means more heat, which burns the contacts further. Eventually the contacts weld shut (pump runs continuously until it overheats and trips the breaker), or they develop so much resistance that the pump cannot start (humming and tripping).
Diagnosing a bad pressure switch is simple. Turn off the breaker. Remove the cover from the pressure switch. Inspect the contacts visually: pitted, blackened, or fused contacts need replacement. If the contacts look okay, use a multimeter to check continuity across the contacts in both the open and closed positions. With the switch manually held closed, you should read near-zero ohms. If you read more than 1 ohm, the contacts are corroded and causing a voltage drop that starves the motor.
Replacing a pressure switch is a 15-minute job that costs $20 to $40 in parts. It should be the first thing you check before calling a well company. Keep a spare on the shelf. They fail without warning, and having the water down while you wait for a part to arrive is worse than the $30 investment in a spare.
Cause #2: Waterlogged Pressure Tank
The pressure tank stores water under air pressure so the pump does not have to run every time you open a faucet. A properly charged tank has an air bladder that is pre-charged to 2 PSI below the cut-in pressure. When the bladder fails or loses its air charge, the tank fills completely with water and has no air cushion. Without the cushion, the pressure drops instantly when any faucet opens, and the pump turns on. When the faucet closes, the pressure rises instantly, and the pump turns off. The pump cycles on and off every few seconds. This rapid cycling is called short cycling.
Short cycling kills pumps and trips breakers for two reasons. First, the starting current of a submersible well pump is 3 to 5 times the running current. Starting 20 to 30 times per hour puts enormous thermal stress on the motor windings. Second, each start cycle dumps a burst of high current through the breaker. Breakers are rated for a certain number of cycles per hour, and exceeding that rating causes the thermal element inside the breaker to heat up and trip even though no single current draw exceeds the breaker rating.
To diagnose a waterlogged tank, turn off the pump breaker and open a faucet to drain the pressure. With the tank at zero pressure, press the Schrader valve on top of the tank (it looks like a tire valve). If water comes out instead of air, the bladder has failed and the tank is waterlogged. If air comes out but the pressure reads less than 2 PSI below the cut-in setting, the tank has lost its charge. Recharge with a tire pump or small compressor to the correct pressure (28 PSI for a 30/50 system, 38 PSI for a 40/60 system).
If the bladder has failed, the tank must be replaced. A typical 20 to 30 gallon residential pressure tank costs $150 to $300 installed. A properly sized tank for a 10 GPM pump should have a drawdown volume (the amount of water it delivers between cut-in and cut-out) of at least 5 to 7 gallons, which prevents the pump from cycling more than 6 to 8 times per hour. Oversizing the tank is always better than undersizing: a bigger tank means fewer pump cycles, longer pump life, and more consistent water pressure.
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Cause #3: Voltage Drop on the Pump Wire
Submersible well pumps are fed by a wire that runs from the pressure switch down the well casing to the pump at the bottom. A 200-foot well with the pump at 180 feet has at least 360 feet of round-trip wire length (180 feet down, 180 feet back). At that distance, voltage drop is a serious concern, especially for single-phase pumps on smaller wire sizes.
Well pump wire is typically sold in specific gauges matched to pump horsepower and well depth. The manufacturer's installation manual specifies maximum wire distances for each gauge. A 1 HP, 230-volt pump on 10 AWG wire is typically rated for a maximum distance of about 400 feet (one way). But that rating assumes the wire is in good condition and the connections are clean. Corroded splices, damaged insulation, and water-infiltrated connections add resistance that effectively shortens the allowable distance.
The symptom of voltage drop on well pump wire is identical to any other voltage drop problem: the motor struggles to start, draws excessive current, runs hot, and eventually trips the breaker. The difference is that you cannot easily inspect 200 feet of wire that is submerged in a well casing. You can, however, measure voltage at the wellhead while the pump is running. If the voltage drops more than 5% from the panel voltage when the pump starts, the wire is undersized or damaged.
If the wire is undersized, the only fix is to pull the pump and replace the wire with a larger gauge. This is often combined with a pump replacement since the labor to pull the pump is the same either way. If the wire is the right gauge but has corroded splices, the splices can be remade with waterproof heat-shrink connectors when the pump is pulled. Use only UL-listed submersible splice kits rated for continuous submersion.
Long-Run Voltage Drop Calculator
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Cause #4: Failed Start Capacitor or Control Box Relay
Single-phase submersible pumps over 1/3 HP use a control box mounted near the pressure tank. Inside the control box is a start capacitor and a relay (or solid-state starting device) that provides the phase shift needed to start the motor. When the capacitor fails, the motor cannot develop starting torque. It hums, draws locked-rotor current, and trips the breaker within seconds. When the relay fails, the capacitor may stay in the circuit too long, overheating the start winding, or it may not engage at all.
Capacitor failure is age-related. Electrolytic start capacitors have a typical lifespan of 5 to 10 years. They degrade gradually, losing capacitance over time, until they can no longer provide enough phase shift to start the motor. A capacitor that has lost 20% of its rated capacitance may still start the motor on warm days but fail on cold mornings when the oil in the pump is thicker and requires more starting torque.
Diagnosing a bad capacitor requires a multimeter with a capacitance function. Turn off the breaker, open the control box, and discharge the capacitor (short the terminals with an insulated screwdriver). Then measure the capacitance. Compare to the value printed on the capacitor. If the measured value is more than 10% below the rated value, replace the capacitor. A replacement capacitor costs $15 to $40 and takes 5 minutes to install.
The relay can also be tested with a multimeter. Check continuity across the relay contacts in both the energized and de-energized states. A relay with pitted or welded contacts will show the wrong continuity reading. Relay replacement costs $30 to $80 depending on the control box model. Some modern control boxes use solid-state starting devices instead of mechanical relays. These are more reliable but cost more to replace when they do fail ($60 to $150).
Cause #5: Actual Pump or Motor Failure
After ruling out the pressure switch, pressure tank, voltage drop, and capacitor or relay, the remaining possibility is that the pump motor itself has failed. Motor failure in submersible pumps usually involves insulation breakdown in the motor windings, which causes a short circuit to ground or between windings. This draws excessive current and trips the breaker immediately or within seconds of starting.
You can test for motor winding failure from the surface without pulling the pump. Disconnect the pump wires at the control box or pressure switch. Using a megohmmeter (megger) or a multimeter set to the highest resistance range, measure the resistance from each motor lead to ground (the pump casing or the green ground wire). A healthy motor should read at least 1 megohm (1,000,000 ohms) to ground. A reading below 50,000 ohms indicates insulation breakdown. A reading near zero indicates a dead short, and the motor is finished.
Also measure the resistance between the motor leads (winding to winding). Compare the readings to the manufacturer's specification. If one winding reads significantly different from the others, that winding is damaged. Uneven winding resistance causes current imbalance, overheating, and eventual failure.
If the motor tests bad, the pump must be pulled and the motor replaced. For wells under 200 feet, this is a half-day job for a well service crew with a pulling rig. For deeper wells, it may take a full day. The cost includes the rig rental or service call ($500 to $1,000), the pump or motor ($400 to $1,200 depending on HP and depth rating), new pump wire if needed ($0.50 to $2.00 per foot per conductor), and a new pitless adapter or torque arrester if the existing one is damaged. Total cost for a typical residential well pump replacement runs $1,500 to $3,500.