Ironically, the ordinary garden hose is the most frequent offender. A garden hose can be extremely hazardous when it is left submerged in swimming pools, utility tubs, soapy buckets, etc. Chemical sprayers attached to hoses for weed killing and fertilizing can also be a concern. Typically, if you don't want to drink it, don't connect your water system to it. However, backflow from hose bib cross-connections can usually be prevented by installing hose bib vacuum breakers that can be purchased at most hardware stores.
Other cross-connection examples include:
- Boiler systems with chemical additives that may back-siphon
- Lawn irrigation systems with submerged nozzles
- Connections between private wells and piping with water supplied by the county