When designing and installing closed-loop ground-coupled heat pumps systems, it is necessary to be aware of applicable environmental regulations. Within the United States, nearly half of the states have regulations specifying or restricting the use of particular antifreezes or other fluids within the ground loop of a ground-coupled heat pump system. A number of other states have regulations pending. While all of these regulations are based on the need to preserve groundwater and/or aquifer quality, the list of acceptable antifreezes varies among those states with specified fluids. Typical antifreezes in use include ethylene glycol, propylene glycol, brines, alcohols, and potassium acetate. Each of these has its benefits and drawbacks. The status of the regulations has been determined for all of the states. An overview of the regulations is presented in this paper, along with a summary of the states' concerns.

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