What kind of glycol or alcohol are used? Ethylene glycol and propylene glycol are both biodegradable. Propylene glycol is not toxic to humans in reasonable quantities. Ethylene glycol is. Ethanol is not toxic to humans in reasonable quantities either. I can't imagine that propylene glycol or ethanol would be a ground water hazard in a ground source loop.

While there is some element of risk, in my estimation this issue is over-blown, particularly in residential installations. You will likely become aware of the problem long before your entire ground loop is depleted. Should a loss of fluid arise, your responsibility would be to properly repair the problem rather than just treating the symptom by 'topping-up' the fluid level.

I would worry more about a neighbor with a buried oil tank, garden pesticides or the neighborhood gas station for that matter.

SR

Thanks for the follow-up information. I may have to assume if it was a bigger issue, it would have more press by now.