Cross Connection Program: Protecting the Quality of Our Drinking Water
Preventing contaminates from backflowing into the water distribution sytem protects public health and ensures safe drinking water.
February 24, 1999
|
Kim Hills, Cross Connection Coordinator, has spent most of his 30 year career preventing and eliminating cross connections that can lead to the contamination of the public drinking water supply. He remembers early in his career when talking to property owners about potential backflow of contaminates into the public water system, hearing emphatically "It has never happened, nor will it ever happen." His years of experience have taught him better. He recalls incident after incident where backflow through a cross connection has contaminated water systems both within a private building and others where the contamination reached the public water system.
First, let’s define some terms. Backsiphonage backflow is when hydraulic conditions within the public water system deviate causing the water to flow in the opposite direction. For example, if a water main broke, or if there is high demand on the water main while fighting a fire (causing low pressure in the main), it's possible for water to flow from a higher pressure system backwards into the main. Under the above conditions when the pressure drops, water can be siphoned from the customer's system (building) into the public water system. If there is a cross connection between the customer's system and the public water system, then the transfer of water has a direct path to the water main. If there are contaminates in the building water system, they can be sucked directly into the public water system. The most common contaminates are anti-freeze from commercial sprinkler systems, carbon dioxide from soft drink carbonation equipment and treatment chemicals from boiler and cooling tower systems. But the possible sources of contamination are almost unlimited.
Another method of backflow is when the pressure within the customer's system is greater than the public distribution system, water can be backpressured from the customer's system into the public water system with the same results. In both backsiphonage and backpressure cases a backflow preventer (a mechanical device) is required to prevent the flow of water from the one system to the other.
Federal law requires water suppliers to protect their water systems from contamination by cross connections. Mr. Hills recalls that there has been enormous progress in protecting the public drinking water supply from contamination. There are literally unlimited potential cross connections between the thousands of outlets in customers’ plumbing and the public water system. Inspections find these cross connections, and the installation of backflow preventers insure that water will not be backsiphoned or backpressured from one system to the other.
Mr. Hills remembers when Salt Lake City first began its cross connection program. "In the 1930s Amber Knight, water engineer, was concerned with private wells that operated at a higher pressure than the City's water system pressure, backpressuring water from the customer's system to the City's water system," recalls Mr. Hills. Continuing, "Mr. Knight mapped out the private wells, and required the owners to either isolate the wells from the City's water system, or disconnect." At this time, little was known about cross connections, but in a sense this was the beginning of Salt Lake City's modern-day cross connection program. During the 1950's there were attempts to regulate high rise buildings with gravity water tanks located on top of the structures. Quirinomous fly larvae were growing in these tanks and there was concern that they could be drawn into the City's water system under backflow conditions. The flies were also found within the various building water systems, and until the source of the problem was found, the building residents blamed the public water supply. Richard F. Sherwood, Sanitary Engineer, took special care to eliminate this problem by working with the building owners.
Concern over backflow prevention came to a head in 1962, when a backflow incident contaminated the airport water system. The U. S. Public Health Service (USPHS) was called in to investigate this interstate carrier facility. Several years later, in 1966, the USPHS conducted a weeklong school for several hundred state, county and municipal officials to train them on cross connection prevention. During that same year Salt Lake City implemented the state's first full time cross connection program. It also was the beginning of a formal state cross connection program. By 1969 cross connection regulations were incorporated into the State Plumbing Code.
Mr. Hills became Salt Lake City's full-time Cross Connection Coordinator in 1972, and has held that position ever since. Before that he was a water treatment plant operator. He has found and eliminated thousands of cross connections through his inspections. He has also tracked down numerous contamination problems. He remembered a situation where a cross connection allowed a commercial fire sprinkler anti-freeze from one building to backflow out of the building and to travel down a dead-end main and contaminate another building's water supply, affecting 15 employees. According to Mr. Hills, "There have been numerous confirmed situations where internal private water systems have contaminated their own system, affecting others within a building." In one large apartment complex a cross connection in one unit caused water contamination in four other units. "In the beginning the customer was convinced that the source of contamination was coming from the City's water system; however after finding the proof, the owner accepted the responsibility," recalled Mr. Hills.
In 1988 the public water distribution system in a 20-block area was contaminated with cleaning solvent, xylene/ethyl benzene typically used for high-pressure engine and parts cleaning. The source of contamination was never found, but a cleaning machine attached to the water system was highly suspected. The particular type of machine used for this purpose, if the check valve failed, could pump cleaning fluid back through the water connection.
Despite the overwhelming proof that cross connections can contaminate the drinking water supply, sometimes it’s still tough to convince building owners to install backflow preventers and to keep them functioning properly through testing. Mr. Hills has been involved in litigation over cross connection regulations and has been to the legislature on numerous occasions to keep cross connection laws in place to protect the public drinking water.
On the lighter side, Mr. Hills recalls the time that a building owner barred him from inspecting his facility and asked him endless questions. It turned out that the owner thought he was an undercover agent from the IRS. Another time, the owner didn't have a business license, and he thought that the cross connection inspection was a ruse to get inside the building.
When asked if he thinks that things are better today than when he first started, he replied, "There is a lot more awareness today. It's taken a lot of effort to elevate this issue over the years." Today there are approximately 600 certified backflow technicians in the state of Utah. "Despite the struggle, its all been worth it," reflects Mr. Hills, "I know because of this program that the water supplied to our customers is safer to drink.”
Questions regarding this can be sent by e-mail to: kim.hills@ci.slc.ut.us