The Backflow Files: School Water Contamination

Welcome to The Backflow Files, a Certified Backflow Testing series where we look at real water contamination incidents, cross-connection failures, and drinking water close calls from around the country. These stories are not shared to scare property owners. They are shared to make backflow prevention easier to understand — because annual testing, proper repair, correct installation, and report submission all exist for a reason.

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Some backflow stories start with a broken valve. Some start with a failed annual test. And some start with a school realizing that a building system and a drinking water system should never have been left unprotected in the first place.

This case takes us to Bowling Green, Kentucky, where in October 2010 an elementary school’s drinking water was contaminated by glycol, a chemical used in the school’s HVAC and geothermal system. During work on the heating and cooling system, a contracting company attempted to pump water from the school’s potable water supply into geothermal pipes. Higher pressure in those pipes caused a small amount of glycol-contaminated water to flow backward into the drinking water system.

That is exactly the kind of cross-connection problem a backflow preventer is designed to stop.

What Went Wrong?

The central problem was simple, but serious: there was no backflow prevention system in place on the HVAC system lines.

Without that protection, the potable water supply was vulnerable when the contractor connected the school’s drinking water to the geothermal piping system. Once pressure built up in the non-potable side, a small amount of chemical-laced water pushed backward into the school’s drinking water.

In this case, the contamination source was not sewage, seawater, or industrial waste. It was glycol from a building mechanical system.

That matters because many cross-connection hazards are hiding in plain sight. Irrigation systems, boilers, geothermal systems, fire sprinkler systems, chemical feed equipment, and HVAC systems can all create contamination risks when they are connected to potable water without the right safeguards.

Reports on the Bowling Green incident say school officials advised students to watch for symptoms and seek medical attention if necessary. Some summaries note that students experienced nausea and were advised to drink milk and seek help if symptoms continued. In other words, this was not just a maintenance issue. It became a public health concern the moment contaminated water entered the drinking supply.

And the entire event appears to have been preventable.

How Was It Fixed?

The immediate correction was to install a backflow preventer on the HVAC system lines so the drinking water supply would be protected from similar backflow in the future.

That is the key lesson here. Once a cross-connection hazard is identified, the fix is not just “clean it up and move on.” The system needs the proper protective device in place so the problem cannot happen again the next time pressure changes or work is performed on the equipment.

The Backflow Lesson

The Bowling Green case is a reminder that backflow prevention is not just for irrigation systems and outdoor assemblies. Building systems inside a property can create just as much risk when they are connected to potable water without proper protection.

For homeowners, businesses, schools, HOAs, municipalities, and property managers, the lesson is simple:

• Any connection between potable water and a non-potable system needs proper backflow protection

• HVAC, boiler, geothermal, chemical, and mechanical systems can all create cross-connection hazards

• Pressure changes can push contaminants backward into drinking water

• A missing backflow preventer can turn routine work into a water contamination event

• Proper installation, annual testing, repair, and retesting help keep that protection in place

Why This Still Matters Today

Most backflow problems do not start with dramatic plumbing failures. They start with overlooked details: a missing device, a bypassed assembly, a temporary connection, a repair that was never finished properly, or a system that was never protected the way it should have been.

That is why backflow testing, repair, installation, retesting, and report submission matter. A backflow preventer is there to stop contamination before it enters the drinking water system, whether the risk comes from irrigation water, fire systems, seawater, chemicals, or glycol in an HVAC loop.

Certified Backflow Testing helps property owners stay ahead of that risk. We provide backflow testing, backflow repair, backflow installation, retesting, and report submission for residential, commercial, HOA, municipal, and property management customers throughout Washington and Northern Idaho.

If you received a notice, had a failed test, need a repair, or want help understanding what is required, call 425-427-8889. We’ll help you get your assembly compliant and your water protection back where it belongs.