In Kentucky, all cross-connections are prohibited as stated in public water supply regulation 401 KAR 8:020, Section 2:
"All cross-connections are prohibited. The use of automatic devices, such as a reduced pressure zone back flow preventer or vacuum breaker, may be approved by the cabinet in lieu of proper air gap separation. A combination of air gap separation and automatic devices shall be required if determined by the cabinet to be necessary due to the degree of hazard to public health. Every public water system shall determine if or where cross-connections exist and shall immediately eliminate them."
All municipalities with public water supply systems should have cross-connection control programs. Those responsible for institutional or private water supplies should also be familiar with the dangers of cross-connections and should exercise careful surveillance of their systems.
What is a cross connection?
Simply put, a cross-connection is any connection to a drinking water supply. These connections may be temporary or permanent between a public water distribution system and any other system containing nonpotable water or other substances. The most common cross-connection in the home is the garden hose attached to the outside faucet. The outside faucet requires a mechanical protection device such as a hose bibb vacuum breaker to prevent possible contamination of the public water supply. Hardware stores sell the home outside faucet assembly with the built-in vacuum breaker.
Defined in Kentucky Administrative Regulation [401 KAR 8:010, Section 1 (14)], cross-connections are physical connections or arrangements between two otherwise separate systems, one of which contains potable water and the other being either water of unknown or questionable safety (or steam, gas or chemicals), whereby there may be flow from one system to the other, the direction of flow depending on the pressure differential between the two systems. As an example, a public water system must not be connected to a private water system or auxiliary water supply without safety devices installed to prevent contamination of the potable water.
Consider this scenario:
It's a hot, sunny, water-using day. You've decided it's time to use the garden hose to spray pesticide on your lawn. Attached to your garden hose is one of those handy bottles that applies the pesticide at the proper rate and dosage when you turn on the faucet. You've taken all the right precautions to prevent yourself from being contaminated by the pesticide by wearing a respirator and gloves. You're spraying the pesticide on your lawn when suddenly your teenager decides to take a midday shower and your spouse turns on the dishwasher and does a load of laundry. The high use of water from your home results in negative reverse flow, allowing the pesticide to be sucked into your home water supply to poison you.
While you are spraying the pesticide on the lawn, a fire erupts down the street. There is a sudden drop in water pressure as water is rapidly pulled out of the mains from the fire department. The pesticide in the garden hose is then drawn into the water mains beyond your home, contaminating the water and causing the entire neighborhood to become suddenly ill and possibly causing death.
A properly installed protective backflow (or backsiphonage) valve could have prevented the contamination and ensuing harm. To prevent contamination from a home faucet, each outdoor spigot should have a hose-bibb vacuum breaker installed.
Plumbing cross-connections are defined as actual or potential connections between a potable and nonpotable water supply. Cross-connections constitute a serious public health hazard, particularly when industry, hospitals, nursing homes or funeral homes do not have adequate cross-connection safety devices installed. There are numerous well-documented cases in which cross-connections have been responsible for contamination of drinking water that, when consumed, caused the spread of disease and even death.