Drinking Water Well Basics

If you do not receive a water bill, chances are you have a private well. It's a good idea to familiarize yourself with your well system, since this is the source of your drinking water.

Typical well system components

Casing: The casing is a tube in the ground that houses the well pump and the pipe that moves water from the pump to the surface. It also prevents the hole from collapsing, and keeps contaminants from entering the water supply. Modern well casings are typically 5" plastic (PVC) pipe.

Cap: The cap is the top of the well casing. The cap must end at least one foot above ground so it is not subject to flooding. The cap usually has a screened vent to prevent insects from entering the well.

Pump: The well pump draws water up the hole and pushes it into the home. The well pump is usually submersible. This means the pump is installed in the well casing several feet below ground, making it operate more quietly.

Pressure Tank: The pressure tank is usually a 3-4 tall cylinder located in the home. It stores water and distributes it through the home at an even pressure. The tank can also serve as additional storage for low-yield wells. The pressure switch located at the tank controls the pumps on/off cycle.

Pitless Adapter: The pitless adapter is a plumbing fitting that attaches to the well casing and routes the water supply line from the pump to the home. It is installed approximately 4 below ground so it is not subject to freezing. Before these were invented, old wells often terminated below ground in pits, or basement off-sets. Pits are no longer necessary, hence the name pitless adapter.

Screen: The screen is at the very bottom of the well, attached to the casing. It keeps sand and gravel out of the well while allowing groundwater to flow into the well. Some wells drilled into bedrock do not need screens since the water travels through crevices in the rock, and there is no sand to filter out.

Well maintenance

Most wells have a long service life of well over 20 years. Follow these tips to ensure a safe supply of drinking water:

  • Keep household chemicals, paint and motor oil away from your well and dispose of them properly by taking them to a recycling center or household hazardous waste collection site.
  • Limit your use of pesticides and fertilizers.
  • Keep your well cap clear of leaves, mulch, dirt, snow and other materials.
  • Use caution when mowing or plowing around your well so you don't damage the well casing.
  • Practice water conservation in your home and install low-water-use appliances.
  • Keep your well records (such as the well construction report, water test results, and maintenance records) in a safe place.
  • Test your water yearly for bacteria (E. Coli).

Common well water issues

Color: Can be caused by decaying leaves, plants, organic matter, copper, iron, and manganese. Not typically health concerns. Aesthetically unpleasing. Water treatment systems can generally greatly improve color or staining issues.

Insects: Old, broken, or missing well caps can allow insects like earwigs to enter the well casing. Insects can bring bacteria into the well, possibly contaminating the water. Insect parts can show up in water, or be trapped in faucet screens.

Odor: Certain odors may indicate organic or non-organic contaminants that originate from municipal or industrial waste discharges or from natural sources. Diesel or gas odor indicates that water should be tested for volatile organic compounds (VOCs). Rotten-egg odor often indicates iron bacteria in the water. Rotten-egg odor could also indicate that the water is high in hydrogen sulfide gas, which can be an issue with some wells in the southeast part of Washtenaw County.

Taste: Some substances such as certain organic salts produce a taste without an odor. Iron and manganese can alter the taste of water. Can cause bitter taste in brewed beverages like tea and coffee. Water treatment systems can generally greatly improve taste.

Grit/Sand: Can indicate that well is failing and has started to pull materials into the well.

Tests for new wells

Once the well is installed, the water must be tested to show it is safe. Sample bottles are available from Environmental Health. New wells must be tested for:

  • Bacteria: Must be negative.
  • Arsenic: Must be 10 parts per billion (ppb) or less.
  • Nitrate: Must be 10 parts per million (ppm) or less.

Tests for existing wells

Homeowners should test the well water for bacteria each year. Other water tests are also available. Different tests may be recommended depending on the water and the home's occupants.

Before a home with a well can be sold, the well system must be inspected and the water must be tested for bacteria, arsenic and nitrate. This is a requirement for the Washtenaw County Time of Sale program.