How Your Well Works
Here is how a well system works, part by part, in plain words. Follow the water from the drilled well to your faucet and learn what each piece does and what failing looks like. Questions or an emergency? Oasis Well Service answers 24/7 at 703-791-3981.
How a Well System Works, From the Ground Up
Most folks never think about their well until the water stops. Knowing how a well system works helps you spot trouble early. So let’s follow the water from the ground to your tap.
The Drilled Well and Casing
Your well is a narrow hole drilled into water-bearing rock. The casing lines the top of that hole and keeps soil and surface water out. A cracked or rusted-through casing can let in dirt, bugs and runoff, and you may see cloudy water or a bad bacteria test after heavy rain. That calls for well casing repair.
The Sanitary Cap
The cap sits on top of the casing. A sanitary sealed cap keeps out insects, rodents and rainwater. A cracked or loose cap is an easy way for contamination to get in.
Down in the Well: Pump, Pipe and Wire
The Submersible Pump
Most homes here have a submersible pump. It hangs inside the well, under the water, and pushes water up. When it wears out you may see pressure that fades, a pump that runs and runs, or no water at all. Ten to fifteen years is the usual life of a well pump, depending on water level, depth, water quality and use. See well pump repair and replacement.
Drop Pipe, Wire and Check Valves
The drop pipe carries water up, and the power wire runs alongside it. Check valves are one-way valves on that line. They hold water up in the pipe when the pump shuts off. A leaky check valve can let the pump kick on when nobody is using water, or cause a bang when it starts.
From the Well to the House
The Pitless Adapter
Below the frost line, the water has to turn sideways and head for the house. The pitless adapter makes that turn through the side of the casing, so the line stays out of the cold and the top of the well stays sealed. When it leaks, you may see water pooling near the well, hear hissing, or have a pump that never shuts off.
The Buried Water Line
A buried line then runs to your basement or crawl space. Roots, shifting ground and old fittings can cause leaks, often showing up as soggy spots in the yard. Both parts fall under water line repair, including pitless adapter replacement and trenching.
Inside the House: Tank and Switch
The Pressure Tank
The pressure tank holds a cushion of air that pushes on the water inside. That gives you pressure between pump runs, so the pump does not start every time you open a faucet. When a tank loses its air, it waterlogs and the pump clicks on and off (short cycling). See pressure tank replacement and our guide to checking tank pressure.
The Pressure Switch
The pressure switch tells the pump when to run. It turns the pump on at the low number (cut-in) and off at the high number (cut-out). Common settings are 30-50, 40-60 and 60-80, and 40-60 is the most common. A worn switch can chatter, stick on, or fail to start the pump. The switch carries line voltage, so never open its cover. That is our job.
Constant Pressure Systems
A constant pressure system uses a controller that speeds the pump up or slows it down to hold one steady pressure. You get even pressure in the shower when someone runs the kitchen tap.
Where Treatment Equipment Fits
Treatment equipment usually goes in after the pressure tank, where the water is under steady pressure. What you need depends on what is in your water, so we start with water testing.
- Sulfur filter: for a rotten egg smell.
- Acid neutralizer: for low pH water that leaves blue-green stains on copper and fixtures.
- Water softener: for hard water and scale.
- UV light: usually last in line, so it sees water that is already filtered. It targets E. coli and coliform. See UV disinfection.
The first three are covered on our water treatment page.
When Something Stops Working
You do not need to know which part failed. Tell us what you see, and we will trace it. Diagnosis is free, within reason. If you have no water, call our emergency line at 703-776-0996. For anything else, call 703-791-3981. Our tips and tricks page lists safe checks you can do first.
Once you know the parts, our well tips and tricks cover the simple checks you can safely do yourself, and the brands we install page explains what we put in when a part needs replacing.
Questions we hear a lot
Where is my well pump actually located?
On most homes here the pump is a submersible that hangs down inside the well, under the water. You will not see it from the basement. What you see indoors is the pressure tank, the pressure switch and the gauge.
What does the casing on my well do?
The casing lines the top of the drilled hole. It holds back loose soil and keeps surface water, dirt and bugs out of your water. If it cracks or rusts through, it can be repaired.
How does water get from my well into my house?
The pump pushes water up the drop pipe to the pitless adapter, which turns it sideways below the frost line. A buried line carries it to the house and into the pressure tank. From there it goes through any treatment equipment and out to your faucets.
What does a check valve do on a well?
A check valve is a one-way valve that holds water up in the pipe after the pump shuts off. When one leaks, the pump may run for short bursts with no water being used, or you may hear a bang when it starts. Call 703-791-3981 and we can check it.
Why is there air inside my pressure tank?
The air is the cushion that gives you water pressure between pump runs. When the tank loses that air, it fills with water and the pump starts and stops over and over. That wears on the pump and switch.
What do the two numbers on a pressure switch setting mean?
The low number is where the pump turns on and the high number is where it shuts off. A 40-60 switch starts the pump at 40 and stops it at 60. Please do not open the switch cover to look, since it carries line voltage.
Where does a water softener or UV light go on a well system?
Treatment equipment usually goes in after the pressure tank. A UV light is usually the last piece in line so it sees water that is already filtered. We test your water first so you only buy what you need.
How is a constant pressure system different from a regular well setup?
A regular setup lets pressure swing between the switch's low and high numbers. A constant pressure system uses a controller that changes the pump's speed to hold one steady pressure. We install Gould, Myers and Grundfos systems.
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