Potassium acetate, methanol, and ethanol have the highest risk of polluting water, with propylene glycol and urea having little risk. Risk of Future Use . From this, it is apparent that methanol use is currently, or may be in the future, limited in many areas. Potassium acetate, because of its leakage problems, may face future regulation, although it is still approved for use in many states. Ethanol is not explicitly approved in some locations, although it meets the criteria of non-toxic and its use is widespread.
Propylene glycol is approved in nearly all states.
While urea and CMA have not been submitted for approval as GSHP anti-freeze solutions, they are used for other applications and it is believed that usage will be allowed. Regulations and approvals . A separate issue, not connected with any specific task, concerns the confusing array of regulations governing the installation of GSHP systems. This in turn often prevents the most efficient and safe anti-freezes from being used in GSHP applications. Three stars indicate that little or no potential for problems has been identified, two stars indicate a minor potential for problems, and one star indicates a major potential for problems.