Residential Drinking Water Well: Well Components (1st in Series)

Knowledge of the main components of a private water well system is an essential first step in ensuring its safe operation. There are three basic types of wells that provide access to groundwater – dug, driven, or drilled. The drilled well can reach confined aquifers, even at significant depths. Confined aquifers tend to have fewer contaminants than shallow aquifers; therefore, they are the preferred type of drinking water well in South Carolina.

A residential well water system includes many components to provide drinking water to a house. The main components of a drilled well, shown in Figure 1, include:

  1. The wellhead is the section that is visible above ground. It should be above the level of possible flood events. The cap must be tightly sealed to keep contaminants from entering the well.
  2. The well is a bored hole connecting the surface to the groundwater. The casing lines the well to keep material from collapsing into it. Most well casing is heavy PVC pipe.
  3. The submersible pump delivers water to the surface.
  4. A screen at the bottom of the well filters out loose soil, such as sand.
  5. A pressure tank provides temporary water storage in a single speed system.
  6. The groundwater must be pumped up the well using a power source– usually electricity.
Figure 1: Diagram of a drilled well.

Figure 1: Diagram of a drilled well.
Image credit: Graphic adapted from Clean Water Store by Katie Collins

Once groundwater is pumped to the surface, additional equipment is necessary for delivery of the water for use. A basic single speed pump system is commonly used; the major components are shown in Figure 2:

  1. A submersible pump stays below the water level in the well and transports water to the surface.
  2. When water reaches the surface, it flows through the wellhead.
  3. A check valve prevents water from flowing back into the well.
  4. A pressure switch regulates the water pressure in the tank. For example, the switch may have a low flow pressure set for 30 psi. When the water pressure drops below 30 psi, the pump will turn on until the tank reaches 50 psi, then turn off.
  5. A pressure gauge is helpful to determine if the switch settings are correct.
  6. Water is stored in a pressure tank.
  7. A separate faucet allows for draining of the tank and access for taking water samples.
  8. The gate valve is used to manually control the flow of water to the house.
Figure 2: Diagram of a single speed pump system.

Figure 2: Photo of a single speed pump system.
Image credit: Photo by Becky Davis edited by Katie Collins

Well-component maintenance mainly consists of observing the operation of the system:

  • Test that the pressure gauge is working properly.
    • Open the faucet (#7 in Figure 2) and note the pressure when the pump turns on.
    • Turn off the faucet and note when the pump turns off. If the gauge needle does not move or is significantly out of range (20-40 psi, 30-50 psi, 40-60 psi are common settings), it is advisable to replace the gauge.
  • The wellhead should also be observed periodically – at least monthly.
    • Check for cracks in the cap or gaps around the edge of the casing to prevent any contamination.
    • Check the electrical wires attached to the wellhead. They must be insulated and free of corrosion.
    • Observe the ground around the wellhead. It should slope away from the wellhead to minimize the flow of potential contaminants into the well.
    • Observe the plant growth around the wellhead. Trees and shrubs should be at a distance of at least 10 feet to minimize root growth, which can cause cracks around the casing.

Two common problems related to a well system include pump failure and water leaks. In the case of a water leak, the first thing to do is turn off the water at the pump (#8 in Figure 2). Then, repair the leak. If the pump fails to turn on, noted by no or low water pressure, it could simply be that the pressure switch is sticking. Often, ants will interfere with the switch. This can be determined by turning off the power to the system and removing the pressure switch cap to see if there is debris or evidence of burning around the electrical contacts. Contacting a professional is best in case the switch needs replacement.

Other observations to make include changes in the landscape that could affect the water quality flowing towards the wellhead, such as new construction, farming enterprises, or animal enclosures.

Additional information on residential wells is available through SCDHEC’s Residential Wells website (, Clemson Cooperative Extension’s Be Well Informed program (, and HGIC 1902, Residential Drinking Water Well: Water Quality, and HGIC 1903, Residential Drinking Water Well: Water Treatment Options.


  1. NGWA Well Owners Guide. Westerville (OH): National Ground Water Association. 2021.
  2. CDC-TABLE Drinking Water Treatment Technologies for Household Use. Atlanta (GA): US Center for Disease Control. 2008 Nov.
  3. Wellcare® information about Water Treatment. Washington (DC): Water Systems Council. [accessed 2 May 2023].
  4. SCDHEC Drinking Water Common Water Quality Problems and Their Treatment. Columbia (SC): South Carolina Department of Health and Environmental Control 2013 Nov.

Related Information

Originally published 10/23

If this document didn’t answer your questions, please contact HGIC at or 1-888-656-9988.

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