Frequently Asked Questions

A cross-connection is when the drinking water supply line is connected to a non-potable substance, like industrial equipment lines or a pool or spa.

Backflow is when a building’s nonpotable water flows in an unwanted direction and back to the City’s clean water supply. This contaminates the clean water and poses a significant threat to health. Industries and businesses that use a lot of water are more at risk of backflow than residences that use considerably less water. Fortunately, there is an effective way to prevent backflow.

Both back pressure and back siphonage in supply lines can cause water to reverse directions and backflow. If the supply line connections are not properly protected, non-potable liquids can be forced into the City’s clean water supply.

• Be aware of potential cross-connections in your water supply and eliminate them.
• Install backflow prevention assemblies where appropriate.
• Repair and replace your backflow assembly when necessary.
• Have your backflow preventer tested annually by a Certified Tester.

Owners must contact a Certified Tester to set up a time to test the backflow preventers, at the owner’s expense. This must be done annually on all backflow prevention assemblies.

The City of Modesto’s Cross-Connection Specialist can help with that. They can conduct a backflow survey at your facility to determine the best backflow preventer for you. You will receive a survey report complete with recommendations. To arrange for this free service, you may call 209-342-2246 or email WaterBackflow@modestogov.com.

Yes, backflow preventers are required on all commercial buildings with a potential cross-connection, according to California Health and Safety Codes 116800 and 116407, Water Codes 13553 and 13578, and Modesto Municipal Codes Article 20 section 9-8.2003  and 11-1.14 sections (g, i, j, k, l, and m).

Backflow prevention assemblies are devices installed at connection points to prevent non-potable substances from flowing back into the drinking water supply. There are various types of assemblies.

An approved backflow assembly is required to be installed at the service connection to protect from potential backflow conditions.

To install a backflow prevention device, contact a licensed contractor. If required, obtain an appropriate building permit. Once installation is complete, contact the cross-connection control staff at the City of Modesto. The City will schedule an initial backflow test for your property, or you can contact a tester on our approved list.

If you had the assembly tested, repaired, or installed, contact your tester or installer to ensure the test report was sent to the City of Modesto Cross-Connection Control staff.

If you did not have the assembly tested, repaired, or installed, please do so to prevent an interruption in your water services.

Water services may be terminated and you may be fined or penalized.