Incidents of backflow occurring

Incidents

Blisters in Alabama

Diagram of backflow incident in Alabama 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 travelled 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.

Backflow Incident – Car Wash

An automatic car wash, which recycles its soapy water for reuse, had a water pump break down. It was a high-pressure pump, which drew reclaimed wash and rinse water from an underground tank and pumps (recycles) it into the initial (scrubber) cycle of the car wash. This cycle is not normally connected to the city’s potable water supply.

After the pump broke down, the piping in the rinse cycle, which operates with city water pressure, was manually connected to the scrubber cycle piping by means of a two-inch hose. This arrangement allowed the car wash to remain in operation.

The pump was repaired the next day, but the two-inch hose (cross-connection) between the scrubber and rinse cycle was still connected. A volume of the reclaimed wash/rinse water had been forced into the city water main through the cross-connection and the car wash’s metered service connection when the pump was restarted.

The incident resulted in many water customer complaints identifying soapy and dirty tap water. If a backflow prevention device had been installed on the car wash metered service connection, the incident could have been prevented.

Fire and Explosion in Connecticut

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.

Diagram of backflow incident in Connecticut

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 vapours.

Because the vapour 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.

Residents sue SAWS over 'recycled water'

Extracted from: Jonathan Bloom, News 9 San Antonio
07/03/2003

Some San Antonio citizens filed a class-action lawsuit against the San Antonio Water System because of a year-old water contamination incident that SAWS once said could never happen.

The problem happened in March 2002, when the Brackenridge Golf Course switched its sprinkler system to "recycled water" - water that's cleaned up at the city's sewage plants, but still not safe to drink. There was a valve - a drinking valve - that was not properly cut and capped. Consequently, when the recycled water was turned on, some of that recycled water did get into the drinking water system.

The problem affected the River Road neighbourhood just behind the golf course. They were getting ill, a lot of digestion and intestinal problems and diarrhoea.

The lawsuit claims it took 2 to 3 weeks for SAWS to acknowledge the problem and correct it. After holding a series of town hall meetings, SAWS paid for some families' medical expenses and replaced some contaminated appliances. Because of those steps, officials at SAWS thought the problem was solved a year ago. But residents in the River Road neighbourhood disagree.

"When you put non-potable treated sewage in drinking water, that is not an issue that easily goes away," River Road homeowner Larry DeMartino said. He is upset that SAWS doesn't consider its recycled water to be dangerous and didn't issue a boil or do-not-drink alert.

SAWS later admit it did the wrong thing by not issuing a boil alert. It received an official judgement and had to pay a fine to the state of Texas. There are over 200 households in the River Road neighbourhood, and more of them could sign into the lawsuit before it goes to court.