What is a cross connection?

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, they are one of the most serious public health threats to a potable water supply system, and many times are present in a residential water system.

It's true! You can pollute your own drinking water without even knowing it. But, by eliminating cross connections, you can help protect the water we all share.

How can backflow occur?

Backflow can occur when either a back siphonage or a back pressure condition exists. Back siphonage backflow occurs when a vacuum is induced on a piping system, just like drinking from a glass with a straw. A garden hose in a car wash suds bucket or a hose submerged in a laundry tub can act as a "drinking straw," allowing undesirable liquids to be drawn through it by back siphonage. Some typical situations which cause back siphonage include:

1. Water main breaks or repairs occurring in the system at a point lower than your water service line.
2. High water flow rates exerted on a water main due to fire fighting, hydrant flushing, large system demands or major piping breaks.
3. Booster pumps taking direct suction from potable water supply piping.
4. Undersized piping in your home.

Whenever the drinking water supply is directly connected to another piping system or process which operates at a higher system pressure, back pressure backflow can occur. Typical causes of back pressure backflow include:

1. Non-potable piping systems equipped with pumping equipment, such as irrigation wells interconnected with a potable system.
2. Steam or hot water boilers.
3. Heat exchangers.

What is the law?

Cross connections with potable piping systems are prohibited by Michigan Plumbing Codes Ordinance. Additionally, Michigan water utilities are required to have a cross connection control inspection program to eliminate and prevent cross connections.

 

COMMERCIAL AND INDUSTRIAL HAZARDS

Common commercial and industrial facilities which may pose a public health threat include:

1. Industries with private wells.
2. Industries with chemically treated boilers.
3. Plating operations, chemical processing plants.
4. Funeral homes, mortuaries.
5. Marina facilities.
6. Hospitals, nursing homes.
7. Research laboratories.
8. Car washes, laundromats.
9. School facilities.

RESIDENTIAL HAZARDS

Many common household uses of water may pose a public health threat to the potable water supply system, including:

1. Hose connections to a chemical solution sprayer to feed lawn/shrub herbicides, pesticides or fertilizers.
2. Lawn sprinkler systems.
3. Chemically treated heating systems.
4. Water softeners.
5. Hose connections to a water outlet or laundry tub.
6. Swimming pools.
7. Solar heating systems.
8. Private non-potable water supplies.
9. Non-code (siphonage) ballcock assemblies in toilets.
10. Water-operated sump drain devices.

This list of potential cross connections hazards is by no means complete, and a home that has any of these situations is seriously jeopardizing its own potable water system and that of the community.

What can be done?

Homeowners, as well as plant managers, businesspeople, administrators and school officials all share the responsibility of protecting potable water systems from contamination through cross connections. Each should contact either the Mt. Pleasant Water Department or the Central Michigan District Health Department for assistance in locating and correcting cross connection hazards. Many residential cross connections can be eliminated by installing a hose bib (faucet) vacuum breaker on each outside hose connection and all hose connections in the basement and laundry room. These devices can be obtained from hardware stores or plumbing supply shops for under $10 each. In other instances, more complex protective devices may be necessary. For these situations, technical assistance in determining what device is appropriate may be needed.