Water well basics: casing, pump and testing

A water well is a drilled hole into an aquifer, lined with casing, fitted with a pump, and connected to a pressure tank that gives the house a steady supply. Private wells are not regulated, so the testing and maintenance that a utility would do become the owner’s job.

The Parts of a Well

A modern residential well has five main components, and each one can fail in its own way.

The borehole is the drilled hole, typically 6 to 10 inches in diameter and 100 to 500 feet deep. It penetrates the water-bearing formation, which may be sand and gravel, fractured rock, or sandstone.

The casing is a steel or PVC pipe that lines the upper portion of the hole and seals out soil and surface water. The seal at the top, called the grout, is the barrier that keeps runoff from running down the outside of the casing into the aquifer.

The screen or open bore is the intake. In unconsolidated formations, a slotted screen holds back sand while letting water in. In bedrock, the hole may be left open.

The pump is usually submersible, hung on a drop pipe near the bottom of the well. A jet pump sits above ground and is used on shallow wells.

The pressure tank stores water under air pressure so the pump does not run every time a tap opens.

How Water Gets to the Tap

The submersible pump pushes water up a drop pipe to the pressure tank. The tank has a bladder with air on one side and water on the other, and the air cushion maintains pressure between pump cycles.

A pressure switch turns the pump on at a low set point and off at a high one, commonly 30/50 or 40/60 psi. When the switch cuts in, the pump runs until the tank reaches the cut-out pressure, then stops.

That cycle is why the tank matters. A tank that has lost its air charge has no cushion, so pressure swings immediately and the pump short cycles, turning on and off every minute. Short cycling wears the motor and is the most common well fault a homeowner can detect without tools.

What a Well Owner Must Do

Private wells are not covered by the Safe Drinking Water Act. No utility tests the water, no agency issues a report, and no one inspects the casing.

The owner’s minimum schedule is annual bacteria and nitrate testing, a broader panel every three to five years, and a visual check of the wellhead for a cracked cap, a sunken area around the casing, or evidence of surface water ponding.

Testing costs $40 to $150 for a lab panel. That is the cheapest insurance in the whole system, and the results drive every treatment decision that follows.

Keep the results in a folder with the driller’s report and any service invoices. When you sell the house, that folder answers the buyer’s first question about the well, and when something changes in the water, it gives you a baseline to compare against instead of a guess.

Common Water Quality Problems

Well water reflects the geology it passes through, so problems cluster by region.

The staging of those treatments matters as much as the choice. Sediment first, then iron, then softening, then carbon, then UV is the standard order, and moving a stage usually costs more in service calls than it saves in fittings.

Well Maintenance

The pump and tank are the mechanical parts, and they have predictable lives. A submersible pump lasts 10 to 15 years; a pressure tank 8 to 12. Both are replaced rather than repaired once they fail.

The casing and grout are the long-lived parts, and they are the ones that determine whether the water stays clean. A cracked casing lets surface water in, which shows up as bacteria that return after every shock chlorination.

Annual testing is how you notice. A well that was clean for a decade and suddenly shows coliform is telling you something about the casing, the grout, or a change in the water table, and the trend is only visible if you have the older results.

Five Steps for a New Well Owner

1. Get the driller’s report with depth, yield, and pump setting.
2. Test the water with a full lab panel before moving in.
3. Inspect the wellhead for a sealed cap and proper grading.
4. Record the pressure switch settings and tank air charge.
5. Set an annual test reminder for bacteria and nitrate.

When to Call a Professional

Call a well contractor if the pump short cycles, pressure at the tank is low with fixtures running, the pump runs continuously, or the water suddenly turns cloudy or sandy. Those point at the pump, the tank, or the screen rather than at treatment.

Call a treatment contractor after the test results are in, not before. Buying a softener for water that turns out to be iron-heavy wastes money, and buying an iron filter for water that is merely hard does the same.

The diagnostic split between supply and treatment is covered in well pump versus treatment, the test schedule in well water testing, and the treatment chain in well water system layout.