You work in plumbing, you maintain a critical set of infrastructure, you already know the importance of keeping these systems running at capacity. Sometimes in our drive to keep things running it can be forgotten just how perilous it can be when things go wrong. In this post, let's take a look at a few stories where things went wrong. With Backflow season right around the corner, we'll focus on stories involving back flow prevention.
The Palm Beach County Health Department issued a notice of violation against the city of Boca Raton for long-standing problems with the city’s drinking water, including the presence of fecal matter. The notice demanded immediate corrective action on four major problems: inadequate cross-contamination safeguards in place to prevent wastewater from entering drinking water, an issue the city had been aware of since 2006; an illegal chemical injection system that had been hooked up to city water lines for eight years; the reconnection of disinfected wells to city lines without adequate microbiological surveys to ensure removal of harmful contaminants; and failure to conduct thorough tests for the presence of lead and copper in water lines.
On January 29, 1981, a nationally renowned fast food restaurant in Norfolk, Virginia complained to the Water Department that customers were rejecting all drinks—including soda-fountain beverages, coffee, and orange juice— because of a salty taste. A check with adjacent water customers revealed another complaint of salty water from a nearby waterfront ship-repair facility. Both the restaurant and the shipyard were served from the same water-main lateral, which stemmed from the main distribution line. Officials promptly conducted a cross-connection control inspection of the ship-repair facility and revealed the following details:
The backflow preventer installed on the service line to the shipyard had frozen and burst earlier in the winter. It had been removed and replaced by a sleeve in order to maintain the water supply to the shipyard, thereby eliminating all protection against backflow.
The shipyard fire protection system consisted of high-pressure seawater maintained by both electric and diesel-driven pumps.
The pumps were primed through the use of a city water line, which was directly connected to the high-pressure fire system. With the priming line left open and the first service pumps maintaining high pressure in the fire-service lines, raw salt water was being pumped under positive backpressure through the sleeve into the public water-distribution system. To correct the problem, the city-water prime line to the pumps was removed and a new backflow preventer was promptly installed at the service line in place of the sleeve. To prevent future freeze-ups, heat tape was wrapped around the backflow preventer.
The absence of a backflow prevention system at an elementary school in Bowling Green, Kentucky allowed glycol, a chemical used in the HVAC system, to enter the drinking water. When a contracting company attempted to pump water from the potable supply into geothermal pipes, pressure caused backflow of a small amount of chemicals into the drinking water. School officials urged students to watch for symptoms and seek medical attention if necessary. To keep the drinking water safe in the future, workers installed a backflow preventer on the HVAC system lines.
In a meat packing plant in Marshalltown, Iowa, $2 million of pork was contaminated by waste water when the wrong pipe was hooked up to a newly drilled well. Plant employees unwittingly sprayed contaminated water on hog carcasses and cuttings during the cleaning process. Sewage water from the kill floor and water used to deodorize rendering operations entered the potable water line due to a cross-connection, concluded food safety and quality service officials. The plant subsequently installed, tested, and maintained backflow preventers—spending more than $3 million resolving the problem and leaving 200 people temporarily out of work.
A pesticide used for termite control was found in the water supply of a northern New Jersey municipality, leaving 63 homes without water. A construction crew inadvertently broke a water main while widening a bridge, and in the two hours it took to repair the break, pest- control chemicals back-siphoned from a pesticide company into the water main. Several hours after workers repaired the water main break, a customer called the Water Department to complain that the water was milky and smelled bad. Officials immediately cut off the water supply to the 63 affected homes and notified them not to drink the water or use it to cook, bathe, or wash clothes. The pesticides (including Dursban, chlordane, heptachlor, and lindane) are not harmful in small doses; however, ingestion of moderate doses triggers vomiting, and large doses cause breathing difficulties— which can be life-threatening. Officials arranged for a tank truck with potable water to be parked in the affected block, and made available shower facilities at the local public schools. Officials then flushed and super-chlorinated the affected water pipes.
As workers at a gas company used water from a private hydrant to purge a tank of propane, they failed to notice that the pressure in the tank (85-90 psi) was greater than the pressure in the water line (65-70 psi). As a result, backpressure backflow pushed propane vapor into the water lines for an estimated 20 minutes—enough gas to fill a mile of an eight-inch water main. The propane contaminated the town water supply, forced 500 people from their homes, and caused fires in two houses.
Clearly, there are a lot of ways for back flow prevention to go wrong, and only one way for it to go right. Whether it's propane or pesticides leaching into the water line, it's gonna be a problem, and nobody wants to be drinking feces, or seawater or glycol. It's why annual back flow testing and maintenance is mandatory. Backflow season is right around the corner, and we're here to help.