Backflow and Cross-Connection Prevention

back flow image

While MSWD works every day to deliver safe and reliable drinking water to its customers, sometimes hazardous conditions may exist on a customer’s property that could potentially risk the safety of the public drinking water system.  

For this reason, backflow and cross-connection prevention is an important part of the District’s water quality program.

California State Water Resources Control Board Title 17 of California Code of Regulations Section 7583-7605 and Section 9, and the District’s Cross Connection Control Ordinance 93-3 requires the installation and annual testing of backflow protection devices whenever a plumbing fixture is connected to the water supply and poses a risk. 

Why is this important?

Water distribution systems are designed to have higher pressure than a customer’s system to keep water flowing in the right direction. However, when there is a drop in pressure in our distribution system, a reverse flow – or backflow – can occur.

This can be caused by incidents such as a severed fire hydrant, high demands such as firefighting, water main breaks, and earthquakes. A backflow condition can result in water contamination if hazardous cross-connections exist, endangering the quality of your drinking water.

What are cross-connections?

Whenever a plumbing fixture is connected to the drinking water supply, a potential cross-connection exists. Some examples include:

  • Hose bibs
  • Livestock watering systems
  • Hose attachments to apply hazardous or harmful substances
  • Lawn irrigation systems
  • Ornamental fountains and ponds
  • Fire sprinkler systems
  • Solar heat systems
  • Wash basins and service sinks

What are hazards? 

MSWD requires all commercial and industrial properties, as well as some residential properties, to install and maintain a backflow prevention device. While single-family residences typically are not generally required to have a backflow device, you can help prevent backflow contamination by:

  • Not leaving hoses attached or submerged in unsafe water
  • Confirming that anti-siphon type valves are installed on irrigation valves
  • Installing hose bib vacuum breakers

MSWD has more than 1,200 backflow prevention assemblies installed within its service territory. All installed devices are tested on an annual basis, and monthly fees associated with these devices are dependent upon the service size.

All backflow prevention devices are inspected and tested annually for proper operation.  Inspection and testing shall be performed by the District's certified inspector or a District-approved private inspector.  The results of each test, including repairs, are recorded on a form maintained by the District.

For more information, please contact Customer Service at 760-329-6448.