How Does a Well Work?

For more than 23 million households, well water is a necessity. Rather than getting water from a city or municipality, well water is drawn from underground sources and delivered to the home via a well system. That’s not the only difference between city and well water though. Unlike municipal water, which is filtered and treated before reaching homes, well water is pulled straight from underground reservoirs and is not treated for any contaminants. It’s up to homeowners to ensure their water is consistently safe to use and consume. But how does a well system work and what keeps clean water flowing to your home’s taps? 

Where Does Well Water Come From?

Private wells tap into water supplies from underground aquifers—layers of porous rock that hold water. Rain and melted snow seep through the soil and accumulate in these formations, naturally forming and replenishing groundwater reserves. The water table, or the top level of the aquifer, fluctuates with rainfall, drought conditions, and seasonal changes. During wet periods, the water table feeding a well rises and makes groundwater more accessible, while the table drops during dry conditions, forcing wells to work harder to pull water from deeper below the surface. 

How Does a Residential Well Work?

A well system is made up of several key components, including the well structure, well pump, and pressure tank. Filtration systems are also critical for well water systems, though homeowners likely need to purchase these systems separately. While filters aren’t necessary for wells to work, they are essential for making sure well water is safe to use. 

Well Construction

A private well must be drilled or dug deep into the ground to reach aquifers. Most residential wells range from 100 to 800 feet deep, though some may extend beyond 1,000 feet in areas where groundwater is only accessible further below the earth’s surface. Well construction includes a well casing, well cap, and well screen.

The well casing is a sturdy pipe, generally made of either PVC or steel. It lines the well to prevent collapse and reduce the risk of contaminants seeping into the water from the surrounding soil. At the bottom of the well is the well screen, a mesh-like barrier that limits larger sand and sediment particles from entering the water supply. The well cap sits on top of the casing and helps keep debris and surface water from entering the well. It also includes a vent to regulate pressure inside the well. 

Water Test and Survey

How Does a Well Pump Work?

The well pump is the component that draws water from underground reservoirs. Depending on how deep a well is, most homeowners either have a submersible or jet pump. Submersible pumps are located inside wells, pushing water to the surface from deeper wells. Jet pumps, on the other hand, are installed above ground. These pumps use suction to pull water up from shallow wells. Some well systems also include a storage tank that holds water before it’s pumped into the house, while others rely on gravity-fed systems.

For more than 23 million households, well water is a necessity.

All well pumps feature a pressure switch. This small yet critical component helps regulate the pump by detecting water pressure. When the pressure falls below a set level, the switch automatically engages the pump to refill the pressure tank. This automation ensures a steady water supply while reducing unnecessary wear on the pump. 

How Does a Well Pressure Tank Work?

A pressure tank stores well water before it reaches household plumbing, allowing for consistent water pressure and reducing strain on the pump. Instead of turning on every time someone in the household runs a faucet or fixture, the pump fills the pressure tank, and the compressed air inside pushes water through pipes as needed. Most modern well systems use diaphragm bladder tanks. These solutions have a flexible rubber barrier separating water from air. As water enters, the air compresses, creating pressure that helps push water out when a fixture is turned on. A check valve, or one-way valve, keeps water pressurized in the tank and stops it from flowing back down into the well. 

Do Wells Need Water Filtration Systems?

A well system on its own doesn’t guarantee that your water is safe to consume. Because well water isn’t treated by local water authorities, well owners are solely responsible for ensuring their water is potable. Groundwater pollutants can enter wells through a variety of methods like runoff or ground contamination and some impurities naturally occur in groundwater. This is why it’s essential for homeowners to test well water on a regular basis and invest in whole house water filters designed to combat any contaminants present. In many cases, it’s simply not enough to purchase only one type of filter; different types of water filters are designed to capture specific impurities. Some common options for well water include:

• Sediment filters: Trap particles like sand, dirt, rust, and other large particulates. 
• Catalytic carbon filters: Reduce chemicals like chlorine, chloramines, pesticides, herbicides, and more than 100 volatile organic compounds (VOCs).
• AIO (air injection oxidation) filters: Used in combination with catalytic carbon filters to decrease iron, sulfur, and manganese levels. 
• UV filters: Use ultraviolet light to kill microorganisms like bacteria, viruses, and parasites. 

Water softeners are commonly part of well systems as well. Salt-based and salt-free water softeners specifically target hard water minerals like calcium and magnesium, either reducing their levels or changing their chemical composition to reduce the effects of limescale buildup.