An Introduction to Cross-Connection Control
In 1974, the Safe Drinking Water Act (SDWA) was established to protect human health from contaminants in drinking water
and to prevent the contamination of existing groundwater supplies. This act and its amendments (1986 and 1996) require
many actions to protect drinking water and its sources. One of these actions is the installation and maintenance of an
approved backflow prevention device at the water service point of connection. These devices are installed whenever a
potential hazard can exist in a given system as the backflow prevention device prevents a cross-connection.
What is a Cross-Connection?
A cross-connection is any connection between your drinking water and any other source of water that combines the two
when a backflow condition occurs; typically resulting in contamination of the water system.
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). There are two situations that can cause the water to go backward (backflow):
- Backpressure – when the pressure in your pipes is greater then the pressure coming in.
- Backsiphonage – when there is a reduction of pressure in the water distribution system.
To protect the water system, there are two types of backflow prevention devices that prevent the backflow of
water. These are required for all customers (typically business/industrial) to prevent a potential hazard from
entering the City’s water system:
- External – to protect the City’s water system from cross-connection occurring on the customer’s
- Internal – to protect the customer from cross-connections ocurring within the system/pipes on theirown system
To keep your drinking water safe, the Cross-Connection Unit staff diligently checks the plans of each new business
for compliance with cross-connection/backflow requirements. This Unit also tests and repairs all external backflow
prevention devises annually and they send notifications to customers of their upcoming annual test.
The City of Modesto takes pride in the quality of drinking water provided to our customers. To ensure the highest
water quality, distribution systems are tested weekly and quality is maintained by ensuring protections at the water
meter/point of connection, with an approved backflow prevention device.
How Can You Help?
- Be aware of potential cross-connections in your water supply and eliminate them.
- Install backflow prevention devices where appropriate.
- ALL backflow prevention devices are to be tested annually at the owner’s expense.
(Modesto Municipal Code 11-1.113 and California Health and Safety Code 116800-116820.)
- Repair and replace your backflow devices when necessary.
Cross-Connection staff are available to help conduct a backflow survey within your facility to determine what type of
backflow prevention device is best to protect your facility and your personnel. You will receive a survey report complete
with recommendations. To arrange for this free service, call (209) 342-2207.