How a well pump works
Most houses in New Boston and the towns around it get their water from a drilled well. Follow the water from a few hundred feet down to the kitchen faucet, run the faucets to watch the pressure cycle, then break the system the ways it breaks.
Right now
- Pressure
- 56 psi
- Pump
- Off
- Pressure tank
- About 0 gallons stored
- Last pump run
- Not yet
- Starts per hour at this rate
- Not enough cycles yet
- Water in the well
- At its resting level
Pressure over the last 5 minutes
Sped up 15×
A hole in the granite with a pump at the bottom.
A drilling rig bores a 6-inch hole through the soil and into the bedrock, often a few hundred feet deep. Steel casing lines the top of the hole and is sealed into the rock, so surface water can't run down the outside. Below the casing the well is bare rock, and groundwater seeps in through cracks.
The pump hangs near the bottom on its drop pipe. It pushes water up to a fitting just below the frost line, then through a buried line into the basement, where a pressure tank and a switch decide when the pump runs.
Fourteen parts in five groups.
Pumping assembly
A sealed electric motor that runs underwater.
A stack of spinning impellers.
Delivery and plumbing
Carries the water up from the pump.
A one-way valve.
A fitting that turns the water sideways out of the casing into the buried line to the house.
Storage and pressure
A steel tank with a rubber bladder inside.
Turns the pump on at the cut-in pressure and off at cut-out, usually 30/50 or 40/60 psi.
Shows the system pressure.
A safety valve that opens and dumps water if the pressure climbs past about 75 psi, for example when a switch sticks closed and the pump won't stop.
Electrical and controls
A three-wire submersible pump keeps its start capacitor and relay up here, where they're easy to reach, instead of down the well.
Waterproof power cable from the house to the motor at the bottom of the well.
Structure and protection
Steel pipe, usually 6 inches across, that holds back soil and surface water.
A rubber guide that fits the inside of the casing.
A sealed, vented cover that keeps out surface water, insects and small animals.
The tank is what lets the pump rest.
On a 40/60 switch, the pump starts when the pressure falls to 40 psi and stops at 60. In between, the pressure tank does the work: air squeezed above the bladder pushes stored water to the faucets, so washing a few dishes doesn't start the pump at all.
A healthy system runs the pump at least a minute each time it starts, which is what motor makers ask for. When the tank loses its air, the pump starts and stops every few seconds instead, and the switch and motor wear out years early.
Two minutes at the tank.
- 1Open a faucet and watch the gauge. It should fall slowly to the cut-in pressure, then climb steadily once the pump starts.
- 2If the needle swings up and down every few seconds, the tank has probably lost its air.
- 3Press the air valve on top of the tank for a second. Air should come out. Water means the bladder has failed.
- 4Check the floor under the tank for water from the relief valve or a rusted tank bottom.
Six common service calls.
Each one shows up in a place you can point to on the drawing and a shape you can see on the pressure chart. Pick one to see what changes and what to ask on the phone.
Waterlogged pressure tank
"The water pressure pulses in the shower, and I can hear the pump clicking on and off."
The bladder in the tank has split, or the tank has lost its air charge. With no air cushion, a glass of water drops the pressure to cut-in and the pump starts, then a few seconds later it hits cut-out and stops. It starts and stops dozens of times an hour, which burns the switch contacts and wears out the motor.
Leaking check valve
"The pump kicks on in the middle of the night when nobody is using water."
The check valve above the pump should hold the water in the drop pipe when the pump stops. When it leaks, the water drains back down the well, the pressure bleeds off with every faucet closed, and the pump restarts on its own.
Burnt pressure switch contacts
"We have no water, and the pressure gauge says zero."
The switch contacts spark a little every time the pump starts. After years of cycling, or much sooner behind a waterlogged tank, they pit and stop closing. The pressure falls past cut-in and the pump never starts.
Failed start capacitor
"No water. The breaker for the well trips, or something in the basement clicks every so often."
A three-wire submersible pump gets its starting kick from a capacitor in the control box on the basement wall. When the capacitor fails, the motor hums at the bottom of the well without turning, the overload trips, and a little later it tries again.
Split drop pipe
"The pump runs all the time and the pressure is weak."
A split joint or a pinhole in the drop pipe sends part of the water straight back down the well. The pump runs, but the pressure climbs slowly and may never reach cut-out, so the pump runs almost without stopping. A worn pump looks much the same.
Well running low
"The water sputters and spits air, then it stops for a while."
Every well refills at its own rate. In a dry August, or while filling a pool, a low-yield well can be pumped down to the pump's intake. The pump sucks air, the faucets sputter, and then the water comes back once the rock refills the well.
Where AI helps the office and the trucks.
"We have no water" is an emergency to the family calling, and it's often a tripped breaker. When the office knows the questions on this page, the phone does some of the diagnosing and the trucks go where they're needed.
"No water" calls sorted before a truck rolls
An after-hours agent asks what the gauge reads, whether the breaker is on, whether the power just came back, and whether the control box hums. A tripped breaker gets talked through on the phone. A dead pump gets the first slot in the morning.
Custom AI agentsWork orders with the details filled in
The tech still makes the call. AI drafts the job notes and asks for what the next visit will need: a photo of the tank label, the pump depth, the switch setting and the amp readings.
AI Cowork trainingA history for every well
Tank age, pump pulls and water test dates kept by address, so a second call from the same house comes with its history. After a storm, the outage calls get grouped and sorted by who has no water at all.
Workmap
This page shows a typical drilled well with a three-wire submersible pump, simplified for learning. The drawing is not to scale, and the pressures and run times come from a simple model. Turn off the breaker before opening a pressure switch or control box. In New Hampshire, pulling or replacing a pump is work for a licensed pump installer.
