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1. What is a Cross-Connection?

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

2. What is a Backflow?

Backflow occurs when the water in your pipes (after the water meter in your building/facility) goes backward (opposite its normal direction).

3. What causes backflow?

There are two situations that can cause the water to go backward (Backflow):

1. Back pressure may cause backflow to occur when the potable supply piping is connected to a system or fixture which exceeds the operating pressure or the supply pressure of the supply piping. Higher pressure can be caused by booster pumps, boilers, pressure vessels, or elevated piping in places such as high rise buildings or tanks. If these connections are not properly protected, potable and non-potable water or liquids can be forced into the potable supply system.
2. Back Siphonage is caused by a reduced pressure in supply piping. Back siphon can be caused by undersized piping, a line repair or break that is lower than a service point, reduced main pressure due to high withdrawal rates such as firefighting or flushing water mains, or a reduced supply pressure on the suction side of a booster pump.

4. What can I do to safeguard my building/facility from backflow?

• 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.

5. How can I get my backflow preventers tested for compliance?

According to Modesto Municipal Code 11-1.113 and California Health and Safety Code 116800-116820 all backflow prevention assemblies are to be tested annually at the owner / water account holder's expense. Be sure to utilize a Certified Tester when performing this task.

6. What Backflow preventer is right for my building/facility?

There are two types of Backflow prevention assembly devices:

1. External - to protect the City's water system from cross-connection occurring on the customer's property
2. Internal - to protect the customer from cross-connections occurring within the system/pipes on their own system

The City of Modesto's Cross-Connection Specialist is available to help conduct a backflow survey within your facility to determine what type of backflow prevention assembly is best to protect your facility and your personnel. You will receive a survey report complete with recommendations. To arrange for this free service you may contact us at 209-342-2246 or via e-mail at WaterBackflow@modestogov.com 

7. Are Backflow Preventers required by law?

Yes. 

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

8. What is a Backflow Assembly?

Backflow assemblies are devices that are installed at the point of connection/service and prevent non-potable substances from flowing back into the drinking water supply. There are various types of assemblies that are specific for certain applications.

9. Why did I receive a letter stating that I need to install a backflow assembly?

You received this letter because an approved backflow assembly is required to be installed at the service connection to protect from potential backflow conditions.

• Contact a licensed contractor for installation.
• Once installation is complete contact the cross-connection control staff at the City of Modesto to schedule the initial backflow test which the city will provide or you can contact a tester on our approved list.
• Obtain an appropriate building permit if required

10. I received a notice of non-compliance that stated I didn't have my backflow tested, repaired, or installed. What do I do?

If you had the assembly tested, repaired, or installed contact your tester / installer to ensure the test report was sent to the City of Modesto cross-connection control staff. If the work has not been completed you need to do so to ensure there is no interruption in your water services.

11. What happens if I do not comply with the requirements?

Non-compliance may result in your water services being discontinued as well as fines and penalties being added.