What a Well Pump Does and Why You Need One
A water well pump is a machine that pulls water from underground and pushes it up to your house. Without it, water stays trapped hundreds of feet below the surface where gravity cannot bring it up on its own. The pump sits inside the well casing (the pipe that goes down into the ground) and does two jobs at once: it lifts the water against gravity and creates pressure to send that water through your pipes to every faucet, shower, and toilet in your home.
Most residential well pumps are submersible pumps, meaning they sit underwater inside the well itself. Some older systems use jet pumps, which sit above ground and pull water up through a pipe. Both types work on the same basic principle: an electric motor spins an impeller (a fan-like wheel inside the pump), and that spinning motion moves water upward and outward.
Key Takeaways
- A submersible pump sits inside the well and uses a spinning impeller to push water up through a pipe to your house.
- The pump motor runs on electricity and is controlled by a pressure tank that turns the pump on when pressure drops and off when the tank fills.
- Water moves through the pump in stages—each impeller stage lifts the water higher, so deeper wells need pumps with more stages.
- A check valve at the pump outlet stops water from flowing backward down the well when the pump shuts off.
- Most residential well pumps last 8 to 15 years before they need repair or replacement.
How the Impeller Pushes Water Upward
The heart of any well pump is the impeller, a wheel with curved blades that looks similar to a fan. When the electric motor spins this wheel at high speed (often 3,450 revolutions per minute), the blades push water outward and upward. This motion creates two things: it moves water physically upward through the pump, and it creates pressure that forces water out through the discharge pipe toward your house.
A single impeller can only lift water so far—roughly 25 feet of vertical rise per stage. For deeper wells, the pump contains multiple impellers stacked inside the same housing, one above the other. Water enters at the bottom, passes through the first impeller, then the second, then the third, each one lifting it higher. A 200-foot-deep well might have a pump with 10 or more stages, each contributing to the total lift. This is why deeper wells require more expensive pumps—they need more impellers inside them.
The Pressure Tank and Pump Cycling
Your well pump does not run constantly. Instead, it is controlled by a pressure tank, a metal or composite tank that sits above ground, usually in a basement or utility room. Inside this tank is a rubber bladder that separates water from air. As the pump pushes water into the tank, the water compresses the air on the other side of the bladder, building pressure.
When the pressure inside the tank reaches a set upper limit (usually around 60 pounds per square inch), a pressure switch tells the pump motor to shut off. When you turn on a faucet or toilet, water flows out of the tank and pressure drops. Once pressure falls to a lower set point (usually around 40 psi), the switch signals the pump to start again. This on-and-off cycling protects the pump from running constantly and gives you steady water pressure throughout your home.
Without the pressure tank, the pump would have to run every time you opened a faucet, which would wear out the motor quickly and create uneven water pressure. The tank acts as a buffer, storing pressurized water so the pump can rest between uses.
The Check Valve Stops Water From Flowing Backward
At the outlet of the pump (where water leaves to go up the discharge pipe), there is a one-way valve called a check valve. This valve allows water to flow upward toward your house but prevents it from flowing backward down into the well when the pump shuts off.
Without the check valve, when the pump stops, gravity would pull all the water that was lifted back down into the well. The pump would have to re-lift that same water the next time it starts, wasting energy and putting extra strain on the motor. The check valve keeps the discharge pipe full of water and ready to flow, so the pump can restart more easily and deliver water faster when you need it.
How Electricity Powers the Pump Motor
Well pump motors are electric and typically run on either 120 volts or 240 volts, depending on the pump size and your home's electrical service. The motor is sealed inside the pump housing and is cooled by the groundwater flowing around it. This water cooling is one reason submersible pumps can run reliably for years—they do not overheat the way an above-ground motor might.
The motor draws power through a waterproof electrical cable that runs down the well casing alongside the pump. This cable connects to a control box above ground, which houses the pressure switch, a capacitor (a device that helps the motor start smoothly), and sometimes a pressure gauge. The control box is what actually turns the pump on and off based on the pressure tank reading.
What Happens When You Turn On a Faucet
When you open a faucet, water flows out of the pressure tank into your home's plumbing. As water leaves the tank, the pressure inside drops. Once pressure falls below the lower set point (typically 40 psi), the pressure switch closes an electrical circuit. This sends power to the pump motor, which starts spinning. The impellers begin pushing water up from the well, and that water flows into the pressure tank, raising the pressure back up.
If you are using water slowly (a trickle from a faucet), the pump may deliver water faster than you are using it, so pressure climbs quickly and the pump shuts off after a few seconds. If you are using water heavily (a shower and a washing machine running at the same time), the pump may run for several minutes to refill the tank. Once pressure reaches the upper set point (typically 60 psi), the pressure switch opens the circuit and the pump stops.
Common Wear Points and Why Pumps Fail
Well pumps typically last 8 to 15 years, depending on water quality, how often the pump cycles, and how deep the well is. The most common failure points are the impeller (which can wear down or crack), the motor bearings (which can seize if the pump runs dry), and the check valve (which can stick or leak).
A pump can fail suddenly if the well runs dry—if the water table drops below the pump intake, the pump sucks air instead of water and the motor overheats. Some pumps have a low-water shutoff switch that stops the motor before damage occurs, but not all do. Sediment in the water can also wear impellers faster, which is why a sediment filter before the pressure tank can extend pump life. If your water pressure drops gradually or the pump cycles on and off more frequently than usual, the pump is likely wearing out and will need service soon.
Frequently Asked Questions
Why does my well pump make noise when it starts?
A clicking or humming sound when the pump starts is usually the capacitor firing to give the motor an initial boost. A loud grinding or squealing noise means the motor bearings may be failing and the pump should be inspected. Occasional water hammer (a loud bang in the pipes) happens when the pump shuts off suddenly and is usually harmless, but a pressure relief valve can reduce it.
What does it mean if my pump runs constantly?
Constant running usually means the pressure tank is not holding pressure—either the bladder has ruptured or the air charge has leaked out. It can also mean the check valve is leaking and water is draining back into the well. A pressure gauge reading will tell you which problem you have. Constant running wears out the motor quickly, so this should be addressed within days.
Can a well pump freeze in winter?
The pump itself, sitting deep underground, will not freeze because groundwater stays above freezing year-round. However, the discharge pipe above ground can freeze if it is not buried below the frost line or insulated. If the pipe freezes, water cannot flow out even though the pump is working. Burying the pipe at least 4 feet deep or wrapping it with heat tape prevents this problem.
How deep can a submersible pump lift water?
A single-stage pump can lift water about 25 feet. Multi-stage pumps can lift water 300 feet or deeper, depending on how many stages they have. A 200-foot well typically needs a pump with 8 to 12 stages. The pump manufacturer will specify the maximum depth for each model.
What should I do if my well pump stops working?
First, check that power is reaching the control box—look for a tripped circuit breaker or a blown fuse. If power is on but the pump will not start, listen for a humming sound from the motor. A hum with no spinning means the motor is stuck and needs professional service. If there is no sound at all, the motor may have burned out. Most well pump repairs require a licensed pump technician.