top of page


A cross connection is a physical connection between a potable (drinking) water supply and a source of contamination or pollution. This connection can occur under certain conditions such as when plumbing is installed, when using certain appliances, or even attaching a hose to a faucet. Cross connections are not easy to discover, but can pose a serious threat to water quality.

What happens when there is a cross connection?

In drinking water pipes, whether in a commercial building or a family residence, water pressure can suddenly drop for a number of reasons. Drops in water pressure can occur during high water use in the home (running all water appliances, showering, watering) or high water use in the distribution system (firefighting, water main break). When these drops of water pressure occur, contaminated water can be siphoned back into your plumbing system through an unprotected cross connection in your home or in the distribution system.

What are some examples of cross connection situations?
  • Water from a toilet tank can be drawn back into the house water supply and possibly into the public water system if the flush valve does not have an anti-siphon device or if the point of entry to the home does not have a double check valve.

  • If a swimming pool or hot tub is filled with a garden hose submerged in the water, pool water can be sucked up the hose into the house water supply and possibly into the public water system.

  • If an insecticide or herbicide dispenser is attached to a garden hose, a pressure drop can cause chemical-laden water to be pulled up the hose and into the house water supply and possibly into the public water system.

  • If a sprinkler system lacks a proper backflow device, dirty water from the lawn can be siphoned back into the sprinkler head, and flow back into the house water supply.

  • If the pressure drops and a private well is connected to a home, water from the private well can contaminate the public groundwater water supply.


Other places where cross connections are possible include: dishwashers, garbage disposals, hand-held showerheads, fountains, boilers, in-home water treatment systems, solar heating systems, soaking tubs in laundry

areas, hose submerged in a horse trough.

What can I do to prevent cross connections from happening?
  • Use proper plumbing devices to prevent any liquid from backflowing into the potable water system.

  • Never submerge or allow hoses in sinks, pools, chemical mixing tanks, etc.

  • Always ensure an air gap is present during any type of watering.

  • Outfit your toilet flush valve with an anti-siphon device.

Always use a licensed plumber certified in cross-connection control for all household plumbing repairs.

bottom of page