Geological Survey Program fact sheet
Missouri Geological Survey Director: Carey Bridges, RG

Geothermal wells, otherwise known as ground source wells, transfer heat from the earth’s ground temperature to a heat pump system to provide energy efficient heating or air conditioning for homes and businesses. During winter the outside air temperature averages about 20 degrees Fahrenheit; however, groundwater stays an average of 55 degrees Fahrenheit. Ground source heat pump systems pump groundwater or other fluids through a buried loop to a heat exchange unit. The heat exchange unit transfers the temperature of the fluid to warm your home in the winter or cool your home in the summer.

Two types of ground source heat pump systems utilize wells: closed-loop and open-loop. Missouri Well Construction Rule 10 CSR 23-5 regulates the construction and plugging of geothermal wells used in closed-loop and open-loop systems. 

Closed loop systems use a loop of fused polyethylene or polybutylene pipe. The pipe is put down boreholes, connected to the heat exchange unit and filled with an approved heat transfer fluid. Approved fluids include inhibited glycol, methanol, ethanol, or water. The remaining open space in the borehole is filled with grout and sometimes clean fill. A closed loop system has a borehole depth limitation of 500 feet and must be grouted full length. Well that are 200 feet or less, the grout plug method is allowed.

Open loop systems use a water well to supply groundwater to the heat exchange unit. The water is either pumped back into the ground through a second well or discharged at the surface. Water disposed to the surface must remain on the landowner’s property. It may not be run to a drainage that leaves the property unless applicable permits are obtained through the department's Water Pollution Control Branch.

The department's Well Installation section offers a number of services that may be helpful regarding geothermal wells in Missouri.

  • Well Information – Our Well Information Management System tool allows you to search our database for well records and permitted heat pump installation contractors.
  • Technical Assistance – We can provide technical assistance and information to industry members and the general public concerning geothermal wells within Missouri. 
  • Variance Requests – A variance request must be submitted when the normal construction standards for a well cannot be met. This may involve increasing or augmenting the construction requirements to ensure protection of the groundwater. Emergency variance requests can be submitted by calling our office directly.
  • Permitting – A non-restricted heat pump well installation permit is required to construct, repair or properly plug a heat pump well in Missouri. A restricted heat pump well installation permit is required for someone, including HVAC installers, to contract these activities or to direct the installation or plugging.

Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

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