PURPOSE: This rule sets standards for openloop heat pump systems that use wells to produce or return groundwater.

1. (1) Open-loop heat pump systems and their installers that utilize existing surface water supply which is plumbed through the heat pump machine and returned to the same surface water supply are exempt from these rules.
2. (2) Open-Loop Heat Pump Systems and Groundwater Supply Wells. An open-loop heat pump uses groundwater produced from wells which are plumbed through the heat pump machine where the heat transfer of the groundwater is accomplished. The groundwater is then utilized at the surface or returned to the ground via a return well. Any newly drilled or reconstructed well utilized for supply or return water must meet the construction standards set out in 10 CSR 23-3. Any well that was constructed before October 1987 that is utilized as the water supply or return for an open-loop heat pump system is exempt from these rules, except that the surface disposal of the water may fall under the Division of Environmental Quality rules and the return of the produced water via a well must meet rules set out in this section.
3. (3) Surface Disposal of Used Water. After the water passes through the heat pump machine, it may be disposed of to the surface only if the water remains on the landowner’s property. It may not be run to drainage that leaves the property unless applicable permits are secured through the Water Protection Program, Division of Environmental Quality. If the heat pump utilizes more than twenty-five
4. (25) gallons of water per minute when it is in operation, surface disposal of the used water is prohibited.
5. (4) Water Return and Supply Wells for Domestic Heat Pump Applications. Water return wells shall meet the requirements set out in 10 CSR 23 Chapters 1, 2, and 3 concerning casing, casing depth, well seal, borehole, grouting, and reporting. The depth of the water return well must not exceed the depth of the water supply well. Water must be returned to the same aquifer, at a similar depth that it was taken from in the water supply well. A sanitary well seal or a pitless adapter may be used, and the water return pipe must extend at least twenty feet (20') below the static water level.
6. (5) Water Return Wells for Nondomestic Heat Pump Applications. Specifications for water return wells in other than domestic applications will be determined on a case-by-case basis by the division, taking into account the water quality and quantity, geology, hydrology and water usage in the area.
7. (6) To drill and construct an open-loop heat pump well or a water return well, the driller must have a nonrestricted water well installation permit.

AUTHORITY: sections 256.606 and 256.626, RSMo 2000.* Emergency rule filed Nov. 16, 1993, effective Dec. 11, 1993, expired April 9, 1994. Original rule filed Aug. 17, 1993, effective March 10, 1994. Amended: Filed Nov. 1, 1995, effective June 30, 1996. Amended: Filed May 17, 2013, effective Dec. 30, 2013.

*Original authority: 256.606, RSMo 1991 and 256.626, RSMo 1985, amended 1991.