Backflow & Backflow Devices

Backflow is the unintentional reversal of the normal direction of flow in a drinking water system that may result in pollution or contamination of the system by a liquid, gas, solid or combination.


What dangers may arise from backflow?

When backflow occurs, the water drawn back into your main water supply may be contaminated. This contaminated water remains in water lines until it is drained from another fixture in your home. A serious health hazard could result when this contaminated water is used for drinking, cooking or bathing.


What is a backflow device?

Any device, method or type of construction that is used to prevent a backflow condition in a drinking water system.


Why do I need a backflow device on my lawn irrigation system?

A cross connection can occur between the potable drinking water and an unknown source through the lawn sprinkler heads. Contaminants from fertilizer, animal feces, etc., can be siphoned back into your potable drinking water through the irrigation heads.


Does this really happen?

Yes! There are documented cases of cross connection incidents throughout the United States.

Why does a backflow device have to be tested yearly?

Any mechanical device may fail and must be regularly checked and tested. According to Ohio Basic Plumbing Code, testable backflow devices are required to be tested annually.


Who do I contact to test my backflow device?

You can find a certified backflow tester in the phone book under plumbing contractors. Some lawn irrigation companies employ certified backflow testers as well. You should get bids from three contractors to test your device, just as you should with any other contractor you would hire.


Why does the Health District charge a $25 fee for tracking backflow devices?

To cover the cost for our office to track all backflow devices for Hamilton County in a computer database and on hard copy files for the water purveyors and the Ohio E.P.A. The cost also covers the expense of mailing yearly reminder letters to our customers to have their devices tested, and we often have to send more than one letter to get a response.


What is back-siphonage?

Back-siphonage is the reversal of the normal direction of flow in the piping due to a drop in supply pressure, a vacuum or a negative pressure in the supply piping.


What is a cross connection?

A cross connection occurs when pipes, fittings, fixtures and/or devices are arranged so that the public water supply is connected to a water system not approved for drinking. Backflow can occur in these types of situations, creating the potential for a polluted or contaminated public water source.


What factors can cause backsiphonage?

The water supply to your home is normally under pressure, but situations such as a water main break, repair of a water main, or water use for fire fighting can cause this pressure to drop. These low pressure situations can cause water to back-siphon. The effect is similar to the sipping of and ice cream soda by inhaling through a straw, which induces a flow in the opposite direction.


What is the most common cause of a cross connection?

Cross connections commonly occur with ordinary garden hoses. Garden hoses connected to the drinking water supply are often attached to applicators that are used for a variety of potentially dangerous activities, including adding pesticides to gardens or cleaning outdoor surfaces.


What can I do to protect my home?

  • If you have a lawn irrigation system, have the system’s backflow device tested yearly.
  • When doing plumbing repairs at home, know when to call in a professional and hire only licensed certified plumbers.
  • Make sure the plumbing contractor obtains all required permits and inspections. You can search for a bonded and registered plumbing contractor on the Health District’s Web site,



If you have any questions concerning permits, inspections or plumbing codes, all Hamilton County Public Health at (513) 946-7854 or visit us online at


Download a printable version of this fact sheet here.


250 William Howard Taft Road
2nd Floor, Cincinnati, OH 45219
Phone 513.946.7800 Fax 513.946.7890