Carmel issues boil advisory after 36-inch transmission main failure; officials say system likely safe

A failure on a 36-inch transmission main early Monday left large sections of Carmel’s west-side water distribution system under low pressure and prompted a precautionary boil-water advisory, city utility staff said.

City utility staff said the connection that failed was a hydrant tee off a high‑pressure transmission main that feeds the west tower. The main lost pressure as crews were working to bleed and isolate the line; the city estimated about 13,000,000 gallons were being used during a roughly four‑hour high‑demand period early that morning, contributing to rapid loss of system pressure in the affected area.

The advisory was issued under state rules because system pressure fell below 28 pounds per square inch (psi) in parts of the distribution network, city staff said. “Once we get below or we know an area drops below 28 PSI, by state regulations, we have to issue a boil advisory,” the utility presenter said. The city said that the advisory was a precaution tied to low pressure, not to known contamination: disinfection systems at the production plants remained operative throughout the event.

Crews isolated the failed connection within about an hour of being on scene and procured temporary water from neighboring Westfield through emergency interconnects. The city said it restored water service into the network and then took multiple bacteriological samples at Indiana Department of Environmental Management–approved sites. Samples were sent to a third‑party lab; the city said the standard microbiological test has a roughly 24‑hour incubation period and expected to lift the advisory the following midmorning after negative results were received.

City officials said the failed hydrant assembly met project specifications when installed but lacked an additional restraining bolt and collar the utility now plans to add to similar installations. Utility staff said crews will inspect and retrofit the other hydrants installed as part of that same contractor project once demand eases.

Officials acknowledged communication failures during the event: the utility does not yet have a live mass‑text/email notification tool tied to customer meter accounts, and more than 15,000 of the city’s roughly 32,000 accounts fell within the advisory area. The city said it relied on social and local media and on partners (including Westfield) to notify residents and is implementing a customer portal that will support targeted alerts when it goes live.

Practical guidance posted by the utility said residents in the advisory area should boil water used for drinking or preparing infant formula until the advisory is lifted; the city also encouraged residents to contact utility staff if they experienced long pressure drops or outages.

Officials said they believed the water itself was likely safe based on continuous disinfection at the plants and the nature of the failure, but they issued the advisory out of abundance of caution and to comply with state testing requirements. The city pledged to publish the laboratory results and a timeline of repairs once testing concluded and to accelerate notification tools for future incidents.

Votes or formal actions were not recorded during the discussion; staff described the event, the response steps taken, and the planned follow‑up inspections and retrofits.