Plumbing board declines immediate approval for Hydratec’s detoxified ethylene glycol for geothermal wells

The Connecticut Plumbing Board voted unanimously to deny approval at this meeting for Hydratec’s “detoxified ethylene glycol” working fluid for geothermal well applications, citing unanswered questions from state health and environmental officials and requests for more toxicology and remediation data.

Mark Stone, representing Hydratec, told the board the fluid — called DTX — “has an NSF approval for incidental food contact,” has been tested for the EPA and reviewed by the FDA, and is already used in the U.K. and in some U.S. projects. Stone said installers, including Dandelion Energy, had asked for permission to use the product because, he said, “it has better thermal efficiency than standard propylene glycol, and it's less costly.”

Board members said the central public-safety question is what happens if a loop containing DTX leaks into groundwater or a private well. Board member Jay Moore urged caution and moved to deny approval until the Department of Public Health and the Department of Environmental Protection review the product’s data and provide guidance. Moore said the board lacked sufficient toxicology and remediation information, and asked the company to provide its LD50 studies, the NSF dossier, and any U.S.-based toxicologist reviews. The motion to deny was seconded and carried unanimously.

Members raised several specific concerns during discussion: whether DTX can be treated in the same way propylene glycol spills are treated, what remediation options exist if drinking-water wells are contaminated, and whether the product’s inhibitor packages and long-term behavior in buried loops could affect seals and pump hardware. Mark Stone responded that, in his view, the product “breaks down faster than the environment than what you're currently using,” and that a small accidental mix with existing propylene glycol would not damage pumps, though he recommended remediation after any inadvertent mixing.

Board Chair Chuck Appleby said the plumbing board’s role is to protect Connecticut groundwater and that the board would prefer to see sign-off from DPH and DEP before allowing any change to working-fluid regulations. Stone said he had been in contact with Jeff Howard at the state and with Jeff Hayman at the International Ground Source Heat Pump Association, and that NYSERDA has approved the product for New York installations.

The board’s denial was procedural: it does not ban further review. Members asked Stone to provide the DTX dossier, the NSF certification, EPA testing (including LD50 data), and any U.S.-based toxicologist reviews. The board said it will await formal input from the Connecticut Department of Public Health and the Department of Environmental Protection before reconsidering any regulatory change.

Votes and formal action: Jay Moore moved to deny approval pending further review; the motion was seconded and passed unanimously.

The board recorded that staff will circulate any additional documents Stone provides to DPH and DEP and that the item may be placed on a future agenda after those agencies respond.