Water and Pollution Control Department

Backflow Tales From Far and Near

BLISTERS IN ALABAMA		Diagram from "Cross-Connection Control Manual", June 1989, U.S. Environmental Protection Agency
An Alabama business was the source of a backflow incident involving sodium hydroxide in October 1986. Sodium hydroxide was hauled in tankers to the business, and they needed to add water to one of the tankers. The normal practice was to add water at the top of the tanker, but at this site, water was added through a connection on the bottom of the tanker because it was easier to add water this way. Adding water to the top would mean they have to climb up on the side of the tanker and drag the hose up to the top which can be pretty heavy when it is full of water. This business was certain that nothing could go wrong because they had a person watching for mistakes.
However, something did go wrong on that day. A water main broke while water was being added to the truck. The truck driver noticed something was not quite right, so he shut off the valve on the water line. He was there; he was paying attention; he noticed the problem; he shut off the valve. So nothing was wrong. Or was it? He had not prevented sodium hydroxide from getting into the eight-inch water main. The broken water main was repaired and put back into service. The sodium hydroxide traveled down the water main until it reached some houses down the road. At 5:00 a.m. the next morning, a man took his usual morning shower. When he got out, his body was covered with tiny red blisters. At 5:50 a.m., he was in the emergency room. He and several other local residents were being treated for chemical burns. The water system was shut down by 7:00 a.m., and service was restored late that night after the water lines were flushed. The following week residents were still worried about their water. They were afraid that there might still be pockets of contamination that were not flushed out. This situation could have been prevented by installing a containment assembly at the water meter in that business site in Alabama.

SOAPY IN SEATTLE
On Saturday, February 10, 1979, a high-pressure water pump broke down at a car wash in Seattle, Washington. This pump recycled reclaimed wash and rinse water and pumped it to the initial scrubbers of the car wash. No drinkable plumbing connection is normally attached to a car wash scrubber system. After the pump broke down, the car wash was able to continue operation by connecting a two-inch hose section temporarily between the potable water supply within the car wash and the scrubber cycle piping. On Monday, February 13, 1979, the high-pressure pump was repaired and the car wash resumed normal operations, but the two-inch hose connection was not removed. The newly repaired high-pressure pump promptly pumped a large quantity of the reclaimed wash/rinse water out of the car wash and into a 12-inch water main in the street. This, in turn, was delivered to the many residences and commercial establishments connected to the water main. Numerous complaints were received by the water department of gray-green and slippery water. Approximately 100 square blocks were affected by this incident.

FIRE AND EXPLOSION IN CONNECTICUT
		Diagram from "Cross-Connection Control Manual", June 1989, U.S. Environmental Protection Agency
Hundreds of people were evacuated from their homes and businesses on an August afternoon in a town in Connecticut in 1982 as a result of propane entering the city water supply system. As a result, fires were reported in two homes, and the town water supply was contaminated. One five-room residence was gutted by a blaze resulting from propane gas "bubbling and hissing" from a bathroom toilet, and in another home a washing machine explosion threw a woman against a wall. Residents throughout the area reported hissing, bubbling noises coming from washing machines, sinks, and toilets. Faucets sputtered out small streams of water mixed with gas, and residents in the area were asked to evacuate their homes. This incident involved repairs to a 30,000-gallon capacity liquid propane tank. To start the repair, the tank was "purged" of residual propane with water. Using water to purge the tanks is preferred over the use of carbon dioxide since it is more positive and will "float out" any sludge in the tank as well as gas vapors. Because the vapor pressure of the propane residual in the tank was 85 to 90 pounds per square inch (psi) and the water pressure in the main was only 65 to 70 psi, propane gas flowed backward into the water mains. It was estimated that the gas flowed into the water main for about 20 minutes and that about 2,000 cubic feet of gas were involved. This was approximately enough gas to fill one mile of eight-inch water main.

BUT THIS IS IOWA . . .
There have also been cases of backflow in Iowa. A meat packing plant in Marshalltown had to destroy $800,000 worth of pork that was rinsed with contaminated water because of a cross-connection. There was also a case of backflow in Nevada, Iowa at a fertilizer plant.
It can happen here in Ames, Iowa.