How Does a Well Work? Learn the Basics!

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Are you moving into a home with a private well? Or are you just considering installing a well at your current home for your own personal water supply?

Whatever the reason for your interest in using or owning a well, you might be curious about how they work. Not all wells work the same -there are different types of well that collect your water in slightly different ways.

I know that learning about wells can be quite overwhelming, as there’s such a lot of information to take in. That’s why I’ve put together this guide. In an easy-to-digest format, I’ve shared the basic information you need to know about:

  • The three most common types of wells
  • The seven main components of a well
  • Well locations
  • Contaminants of concern in well water

By the end, you should know enough about wells to continue your research, properly understand your home’s well system, or begin the process of searching for a new well for your home.

πŸ’§ Where Does Well Water Come From?

Well water is typically supplied by groundwater, or water that comes from an underground location, like a spring or water-bearing formation.

When it rains or snows, this water seeps through the earth and sits in porous materials, like sand, clay and gravel. These materials can collect a lot of water over time, and this results in the formation of an aquifer.

Deep wells are generally located near underground aquifers, which gives them constant access to a water source deep beneath the surface, known as the water table.

Some wells, like shallow wells, may also get their water from above-ground water sources.

πŸ“ Types of Wells

There are three types of wells you’re most likely to come across in the US: drilled wells, driven wells, and dug wells.

Types of Wells
Source: United States Geological Survey (USGS)

Drilled Wells

Rotary drilling or percussion machines are used to construct drilled wells. A drilled well involves boring a hole thousands of feet beneath the ground. Either the upper part of the well, or the entire well, is lined with casing, which prevents the borehole walls from collapsing and provides housing for the pump and pipe that leads water back to the surface.

The advantage of drilled wells is that their contamination risk is lower, because of their depth. Drilled wells with continuous casing are especially low-risk.

Driven Wells

When a pipe is driven into the ground to construct a well, the well is known as a driven well. This type of well is also cased continuously, but is typically much shallower than a drilled well. Rather than being thousands of feet deep, a driven well is usually between 30 and 50 feet deep.

Driven wells are cased, which does help to prevent some contamination. However, because they draw water from aquifers closer to the surface, they’re more likely to experience contamination than a drilled well.

Dug Wells

Dug wells, otherwise known as bored wells, are shallow wells that are dug into the ground using a backhoe or shovel. These wells have a casing made from tile, stone, brick, or a similar non-porous material to keep them sturdy.

Dug wells have a larger diameter than driven and drilled wells. They don’t typically have continuous well casing, and they’re usually between 10 and 30 feet deep.

πŸ“Œ Components of a Well


The tube-like structure used to transport water from the well to your home is known as casing. Well casing is inserted inside a drilled well, and supports the well stream. The area between the untreated sides of the well and the casing is filled with concrete, which prevents the casing from moving and sets it permanently in place.

Casing is required to keep excess water and dirt from entering the well. This helps to prevent contamination of your drinking water. Though it varies state by state, your well casing will usually need to be a certain length, and your local geology may dictate the material that can be used for your casing. Stainless steel, carbon steel and plastic are commonly used to make well casing.

Well Caps

Think of a well cap like the cap on a bottle. It seals the casing, preventing large particles of sediment, insects, and even small animals from contaminating the well. It also acts as a safety feature, blocking off the well from anyone above-ground.

Well caps are installed on the top of the well, and are made from either plastic or aluminum. Some well caps also require a vent, which is used to regulate pressure when water is pumped from the well.

Well Screens

A well screen sits at the very bottom of the casing, and “screens” the water, preventing large sediment and sand from entering the well when water is pumped in.

The screens in modern wells are typically made from stainless steel, and are available in a range of slot sizes and diameters, from 0.25 millimeters to 3 or 4 millimeters.

Pitless Adapter

A pitless adapter is a type of fitting that is installed about 6 or 7 feet below ground in the well casing, and carries water through a service pipe to the surface. With a pitless adapter, your well should maintain a frost-proof, sanitary seal.

Basic Components of a Well
Source: United States Geological Survey (USGS)

Jet Pumps

If you have a shallow well of 25 feet or less, it probably uses a jet pump. A jet pump is installed on the ground above the well, and sucks water up from the well.

Submersible Pumps

If you have a deep well, on the other hand, you probably use a submersible pump. This type of pump is installed inside the casing of your well, and is hooked up to a surface power source.

Pressure Tank

A well pressure tank has several important purposes: it stores water and provides enough water pressure when your well pump isn’t running; and stores a reserve water supply, allowing the pump to start and stop less often, prolonging its lifespan. Additionally, when your water is in high demand, a pressure tank will give you instant access to water.

A pressure tank contains compressed air, and this is what allows it to deliver water under pressure. The greater the compression, the stronger the pressure. The pressure lowers when water in the tank is used. Eventually, the water pressure will reach a preset pressure – usually between 20 and 40 PSI – and the pump will turn on to refill the tank.

πŸ—ΊοΈ Well Location

The location of a well is something that should be considered carefully to ensure the safety of your water system.

It’s important that a well is installed in a spot where rainwater will flow away from it, rather than into it. Surface water can pick up dangerous pathogens and chemicals from the ground, and if this water is able to pool around your well, it could flood the well and seep into the system.

Proper well construction is also essential to a long-lasting well that you can trust to supply safe, sediment-free water long into the future.

Well Location
Source: United States Geological Survey (USGS)

The exact recommended construction of your well water system will depend on your location. Your local area’s groundwater and geological conditions will determine the safest materials to use in your well construction, which will prevent impurities from entering the well through cracks and poor fittings.

Your local health department should have plenty of information on well construction. Well water system professionals can also ensure that your new well is constructed safely, or that an old, existing well meets the current guidelines.

It’s important to ascertain that the contractors who carry out well drilling and pump installation are insured and bonded. Licensing and certification may also be mandatory for contractors who work on well water systems in your state.

βš›οΈ Contaminants of Concern in Well Water

Even a properly constructed well can become contaminated with concerning impurities. Depending on where you live, your groundwater may contain agricultural chemicals like pesticides and herbicides, heavy metals, gases and minerals, and other environmental contaminants.

Some well water impurities are dangerous to health, while others are damaging to your home, and can give water an unpleasant taste or smell.

Common contaminants of concern in well water systems include:

  • Sulfur
  • Manganese
  • Iron
  • Nitrate
  • Coliform bacteria
  • Zinc
  • Pesticides & herbicides
  • Radon
  • Arsenic
  • Volatile organic compounds (VOCs)
  • Radionuclides

Well water isn’t regulated by the Environmental Protection Agency (EPA), and it’s the responsibility of the well owner to treat their well water, if required, and remove any dangerous drinking water impurities. You can use a well water filter to remove some of the most common impurities listed above.

  • Brian Campbell
    President & CEO, CWS, CWR

    Brian Campbell, a WQA Certified Water Specialist (CWS) and Certified Water Treatment Representative (CWR) with 5+ years of experience, helps homeowners navigate the world of water treatment. After honing his skills at Hach Company, he founded his business to empower homeowners with the knowledge and tools to achieve safe, healthy water. Brian's tested countless devices, from simple pitchers to complex systems, helping his readers find the perfect fit for their unique needs.

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