A cross connection is a physical connection between a potable (drinkable) water supply and a source of contamination or pollution. This connection can be created when plumbing is installed, when using certain appliances, or even simply by attaching a hose to a faucet. Cross connections are not easy to discover, but can pose a serious threat to water quality.
Below are some frequently asked questions about cross connections.
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What can go wrong?
Water pressure in a building's or home's plumbing can suddenly drop for a number of reasons. If the shower, clothes washer, dishwasher, or other water-using appliances are all using water at once, the pressure can drop. If there is high water use in the neighborhood, such as from fire fighting or a water main break, the pressure in your home may drop. When water pressure suddenly changes, contaminated water can be siphoned back into your plumbing system through unprotected cross connections within your home.
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Where are cross connections found?
Cross connections can be found anywhere the public water supply connects with residential or commercial plumbing systems. Here are some common examples of what can happen when cross connections are found in homes:
- Water from the toilet tank can be drawn back into the house water supply if the flush valve does not have an anti-siphon device.
- 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.
- 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.
- 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.
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, filling or draining waterbeds with a hose.
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What should I do to protect myself?
Be aware of situations where your home water supply does or could contact nonpotable liquid. Don't let a cross connection be made if another safer way is possible. If the cross connecting cannot be avoided, use the proper plumbing device to prevent any liquid from backflowing into the potable water system. For example, a hose bibb (outside faucet) vacuum breaker is a simple, inexpensive plumbing device you attach to the faucet before attaching the hose. Other situations require a special backflow prevention device that will isolate potable water from potential contamination. To protect the quality of tap water in your home:
- Never allow hoses to be submerged in sinks, pools, chemical mixing tanks, etc.
- Be sure your toilet flush valves have an anti-siphon device.
- Make sure any plumbing work done in your home is by a licensed plumber certified in cross connection control.
- Contact Denver Water for any additional information. Call 303-628-6000 and ask for the Quality Control Section.
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What is Denver Water doing to protect the public water supply?
Denver Water's most important job is to deliver safe, high-quality water to your home. Denver has adopted a state-required and state-approved Backflow Prevention and Cross Connection Control Program. Industries throughout our service areas are inspected to identify, eliminate or protect (with the proper devices) any cross connections present.
All homes have the potential to contain cross connections. They can be a serious health hazard. Our cross connection control professionals can help identify them and what type of backflow prevention device is needed.