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The Roanoke Incident, Garden Hoses and Backflow
In October, 1979, an incident occurred in Roanoke that unfortunately made that city the Virginia “poster child” of the potential hazards of backflow. Thirty years later, it is a situation that is well-known among water system administrators and operators throughout the state, and it is still discussed at conferences that involve backflow.
An exterminator was treating a home for termites using the insecticide chlordane. He followed his normal procedure of mixing the chlordane solution on site using a 55 gallon drum on his truck as a mixing tank. Water was used from an outdoor faucet at the house, through a standard garden hose, to dilute the concentrated chlordane. The end of the hose was immersed in the pesticide solution. Some time after mixing began, the exterminator returned to his truck to check the drum. He noticed that some of the chlordane mixture had been siphoned out of the drum and into the water system.
At the time this happened, city water department personnel were repairing a nearby water line. The repair resulted in a significant drop in water pressure that, in turn, caused water, including the chlordane solution, to backsiphon into the city water main. As a result, the plumbing systems of 21 houses on an isolated, dead-end section of the city were contaminated with chlordane. The city undertook an extensive flushing program, but eventually replaced all water mains throughout the affected area, as well as the water heaters in each of the homes.
The entire incident could have been prevented if a simple device called a hose bib vacuum breaker had been attached to the faucet. Backsiphonage would have been avoided. The houses in this section of Roanoke had been built some 15-20 years before the city building code required faucet vacuum breakers on new construction. On older construction, the inexpensive device could have been added to the faucet.
The large majority of backflow incidents in residential neighborhoods involve the use of a garden hose. For this reason, a state-wide building code has required all houses built since 1988 to have hose bib vacuum breakers on all outdoor faucets. If you do not have this type of outdoor faucet, the Albemarle County Service Authority strongly recommends that you purchase a hose bib vacuum breaker for each of your outdoor faucets. These are available at any plumbing supply store and can easily be attached to your faucets.
Even with hose bib vacuum breakers in place, care should always be taken when using the garden hose for anything other than watering and rinsing:
- Do not leave a garden hose immersed in any solutions, such as a puddle in the yard or garden, in a tub of soapy water, in a vehicle radiator, in a swimming pool, or in a drain of any kind. In general, do not leave a hose immersed in anything you would not want to drink.
- Remove any garden hose from its connection at the faucet when not in use.
- Containers of granulated fertilizer or herbicide (weed-killer) that can be attached to a garden hose should be avoided if possible. Such solutions can carefully be mixed in a bucket or watering can (without leaving the end of a hose immersed in the solution).
- Indoor hoses should also never be left immersed in sinks, laundry tubs, or basins.
If you wish to better understand this somewhat complicated topic, see the related article “Understanding Backflow and Cross-Connections.”
If you feel you have had a backflow incident, or have any further questions, please contact Peter Swartz at 977-4511, ext. 117 or at pswartz@serviceauthority.org or Tim Brown at 977-4511, ext. 119 or at tbrown@serviceauthority.org