A cross connection is an arrangement of piping which could allow undesirable water, sewage, or chemical solutions to enter your drinking (potable) water system as a result of backflow. Cross connections with potable piping systems have resulted in numerous cases of illness and even death.
Historically, cross connections have been one of the most serious public health threats to a drinking water supply system, and many times are present in a residential water system.
What is backflow and how can it occur? Backflow is the reversal of normal flow in a system due to back-siphonage or backpressure. Back-siphonage backflow occurs when a vacuum is induced on a piping system, just like drinking from a glass with a drinking straw. A garden hose or a hose connected to a laundry tub can act as a drinking straw allowing undesirable liquids to be drawn through it by backsiphonage. Some typical situations which cause back-siphonage action include:
- Water main breaks or repairs occurring in the system at a point of lower elevation than your service point;
- High water flow rates exerted on a water main due to fire fighting, hydrant flushing, large system demands or major piping breaks;
- Booster pumps taking direct suction from potable water supply piping; or
- Undersized piping
Whenever the drinking water supply system is directly connected to another piping system, process that operates at a higher system pressure, backpressure backflow can occur. Typical causes of backpressure backflow include:
- Non-potable piping systems equipped with pumping equipment (irrigation well interconnected with a potable system, for example);
- Steam or hot water boilers; or
- Heat exchangers
What is the law? Cross connections with potable piping systems are prohibited by state plumbing codes. Additionally, Michigan water utilities are required to have a cross connection control inspection program of their water customers to eliminate and prevent cross connections. Common commercial and industrial users posing a public health threat include:
- Industries with private wells;
- Industries with chemically treated boilers;
- Plating operations, chemical processing plants;
- Funeral homes, mortuaries;
- Marina facilities;
- Hospitals, nursing homes;
- Research laboratories;
- Car washes, laundromats; and
- School facilities
Most utilities have made inspections of these facilities and have had corrective action taken where necessary. However, due to a lack of staff resources, many utilities cannot effectively carry out a residential cross connection inspection program. Consequently, residential water users could remain a potential health threat to the public water supply and to other system customers.
What hazards threaten the homeowner? Many common household uses for water pose a public health threat to the potable water supply system whether the home is supplied by municipal water or by a private well. Principal areas of water use in the home that pose threats due to cross connections are:
- A hose connection to a chemical solution aspirator to feed lawn/shrub herbicides, pesticides, and fertilizers;
- Lawn irrigation systems;
- chemically treated heating systems;
- Water softeners;
- Hose connections to a water outlet or laundry tub;
- Swimming pools;
- Solar heating systems;
- Private non-potable water supplies;
- Non-code (siphonable) ball cock assemblies in toilets; and
- Water-operated sump drain devices.
This list of potential cross connection hazards is by no means complete. A private residence that has one or two of these situations is seriously jeopardizing its own potable water system and that of the community if it is served by a public water supply system.
What can be done? Homeowners as well as plant managers, business persons, administrators, and school officials all must share the responsibility to protect potable water piping systems from contamination through cross connections. Each should contact either the local water utility or the local health department for assistance in locating and correcting cross connection hazards. Resident=s supplies by private well sources must assume total control of their water system and safeguard it from contamination. In many instances involving residential cross connections, the installation of a hose bib (faucet) vacuum breaker can prevent back-siphonage of contaminants and provide adequate protection of the homeowners water system and consequently, the utilitys water system.
This means equipping each outside hose connection and hose connections in the basement and laundry room with a simple and inexpensive vacuum breaker. These devices can be obtained from hardware stores or plumbing shops for under $10 each. In other instances, more elaborate protective devices may be necessary. For those situations, assistance in determining what device is appropriate may be needed.