What a well pump does and why it matters
A well pump is the machine that pulls water from underground and pushes it up to your house. Without it, water stays in the ground — the pump is what makes the system work. Most residential well pumps sit inside the well itself, submerged in the water, and they run on electricity. When you turn on a tap, the pump starts automatically and delivers water at pressure strong enough to reach every fixture in your home.
Understanding how your pump works helps you spot problems early, know when to call a professional, and make sense of what a technician tells you. You do not need to repair it yourself, but knowing the basic steps — how water gets pulled up, how pressure builds, and what triggers the pump to run — takes the mystery out of a system that most homeowners never see.
Key Takeaways
- A submersible pump sits inside the well and uses an electric motor to spin an impeller, which forces water upward through a pipe to your home.
- A pressure tank stores water and air under pressure so the pump does not have to run every time you use a small amount of water.
- A pressure switch turns the pump on when pressure drops below a set level (usually around 40 pounds per square inch) and off when it reaches the upper limit (usually around 60 psi).
- The pump runs on 240-volt electricity and draws significant current, so a dedicated circuit and proper breaker are essential for safety.
- Most well pumps last 15 to 25 years, and common problems include loss of pressure, the pump running constantly, or no water at all.
The submersible pump: motor, impeller, and the push upward
The pump itself sits at the bottom of the well, sealed in a long cylinder that fits inside the casing. Inside that cylinder is an electric motor connected to a series of spinning parts called impellers. When you turn on a tap, electricity flows to the motor, the motor spins, and the impellers spin with it. Each impeller is shaped like a small fan or paddle wheel.
As the impellers spin, they force water outward and upward through a series of chambers inside the pump. Each stage of impellers pushes the water a little higher. The deeper the well, the more stages the pump needs — a 100-foot well requires a different pump than a 300-foot well. The pump pushes water up through a single pipe (called the drop pipe) that runs from the pump at the bottom all the way to the surface and into your house. The whole process happens in seconds, and the water arrives at pressure — not just trickling out, but flowing hard enough to fill a bathtub or spray from a shower head.
How pressure builds and the pressure tank's role
The pump creates pressure by forcing water into a closed system. At the surface, water enters a pressure tank — a metal or composite cylinder that holds both water and air. The tank is not completely full of water; it contains a rubber bladder or diaphragm inside that separates water from air. As the pump pushes water in, the air gets compressed, and that compressed air pushes back on the water. This pressure is what makes water flow out of your taps.
The pressure tank serves two purposes. First, it stores water so the pump does not have to run every time you use a small amount — if you wash your hands and use a gallon of water, the tank pressure drops slightly, but not enough to trigger the pump. Second, it smooths out the pressure in your system. Without a tank, the pump would turn on and off dozens of times a day, which wears it out faster and causes pressure spikes that can damage fixtures.
Over time, the air in the tank can dissolve into the water or leak out through the bladder. When this happens, the tank fills completely with water and loses its cushioning effect. You may notice the pump running more often or pressure fluctuating. A technician can check the air pressure in the tank (it should be about 2 psi below your pump's cut-in pressure) and add air if needed, or replace the bladder if it has failed.
The pressure switch: when the pump turns on and off
A pressure switch is a straightforward electrical device mounted on the pressure tank or on the plumbing near it. It has two settings: a lower pressure at which the pump turns on, and an upper pressure at which the pump turns off. Most residential systems are set to turn on at 40 psi and off at 60 psi. This 20-psi range is called the differential.
Here is how it works in practice: you turn on a shower, water flows out, and pressure in the tank drops. When pressure falls to 40 psi, the switch closes an electrical contact, sending power to the pump motor. The pump runs and pushes water back into the tank, raising the pressure. When pressure reaches 60 psi, the switch opens the contact, cutting power to the pump. The pump stops, and the compressed air in the tank continues to push water to your fixtures until pressure drops to 40 psi again, and the cycle repeats.
If the differential is too narrow, the pump cycles on and off constantly, which shortens its life. If it is too wide, you may experience low pressure at the tap. A technician can adjust these settings, though most homeowners never need to — the factory settings work for typical homes. If your pump is running constantly or not running at all, the pressure switch is often the culprit.
Electrical supply and safety
Most residential well pumps run on 240-volt electricity, the same voltage that powers an electric dryer or air conditioner. The pump draws a large amount of current when it starts — sometimes 20 to 30 amps — so it must have its own dedicated circuit breaker in your electrical panel. This breaker is usually 30 or 40 amps, depending on the pump size. The wire running from the panel to the pump must be heavy enough to handle that current without overheating.
The pump also has a pressure relief valve that protects the system if pressure builds too high. If the pressure switch fails and the pump keeps running, or if a valve gets stuck closed, pressure can climb dangerously. The relief valve opens automatically and lets water out, preventing damage to the tank and pipes. This is a safety device and should never be removed or disabled.
Never attempt to repair electrical connections on a well pump yourself. If the pump is not running, the circuit breaker has tripped, or you smell burning near the pump, turn off the breaker and call a licensed well technician or electrician. A well pump failure is not an emergency you can fix with a wrench — it requires professional diagnosis and replacement.
Common problems and what they mean
If your pump stops delivering water, the problem could be a tripped breaker, a failed pressure switch, a broken pump, or a clogged intake screen at the bottom of the well. A technician can diagnose this by checking voltage at the pump, listening for the motor to hum, and testing the pressure switch with a multimeter. Do not assume the pump itself is broken — often it is a simpler fix.
If the pump runs constantly, the pressure switch may be stuck, the pressure tank may have lost its air charge, or there may be a slow leak somewhere in the system. A leak can be as small as a dripping outdoor faucet or as large as a cracked pipe underground. A technician can pressurize the system and listen for the sound of escaping water, or use a water meter to measure whether water is flowing when nothing is turned on.
If water pressure is low, the pump may be losing its prime (air has entered the intake), the pressure switch may be set too low, or sediment may have clogged the pump intake. Low pressure can also mean the pump is straightforward old and worn — impellers wear down over time, and a 25-year-old pump will not push water as hard as a new one.
How long a well pump lasts and when replacement is likely
A well pump typically lasts 15 to 25 years, depending on water quality, how often it runs, and how well it has been maintained. Water with high mineral content or sediment wears out pumps faster. A pump that cycles on and off constantly because of a faulty pressure switch or tank will fail sooner than one that runs normally. Regular maintenance — checking the pressure tank air charge every few years and having the system inspected annually — can extend the pump's life.
When a pump fails, replacement is the only option. Repair is rarely worth the cost. A new submersible pump, installed by a technician, typically costs between $1,500 and $3,000 depending on the well depth and pump size, though costs vary by region and local labor rates. If your pump is more than 20 years old and starting to show signs of wear — low pressure, frequent cycling, or occasional loss of water — it is worth having a technician inspect it so you are not caught without water on a weekend or holiday.
Frequently Asked Questions
Why does my pump run even when I am not using water?
The pressure tank has probably lost its air charge, so it fills completely with water and cannot cushion pressure changes. When a small amount of water leaks out somewhere in the system, pressure drops quickly, triggering the pump to run. A technician can check the tank air pressure and refill it, or replace the bladder if it has failed. A slow leak — even a dripping outdoor faucet — can also cause constant running.
What does it mean if the pump hums but no water comes out?
The motor is running but the pump is not moving water, usually because air has entered the intake line or the pump has lost its prime. This can happen after a power outage or if the water level in the well drops below the intake. A technician can re-prime the pump by filling the intake line with water. If the well is running dry, you may need to wait for the water table to recover or have the pump lowered deeper into the well.
Can I turn off my well pump to save electricity?
No — turning off the pump means no water to your home. If you are leaving for an extended period, you can turn off the breaker to prevent the pump from running, but you must turn it back on before you return. Some people install a timer or switch for seasonal homes, but this requires a licensed electrician to may support it is done safely and does not damage the pump.
How do I know if my pressure tank needs to be replaced?
If the pump is running constantly, pressure is unstable, or the tank is visibly rusted or leaking, it likely needs replacement. A technician can also tap on the tank — if it sounds hollow and full of water rather than having a solid thud, the bladder has failed. Pressure tanks typically last 5 to 15 years depending on water quality and use.
What should I do if my well pump stops working?
First, check that the circuit breaker for the pump has not tripped — if it has, flip it back on. If the pump still does not run, listen for a humming sound at the pump itself; if you hear nothing, there is an electrical problem. Do not attempt repairs yourself. Call a licensed well technician who can test the electrical connections, pressure switch, and pump motor to find the cause.