Backflow Prevention

Federal and State regulations require public potable water supplies to adopt rules to prevent contamination in their water systems. To comply with these mandates, the San Marcos City Council has adopted an ordinance, the Cross Connection Control and Backflow Prevention Program, to protect the City's potable water supply from contaminants back-flowing from a customer's water system. Article 9, Chapter 86 of the City Code establishing this program was approved August 13, 2001 (See the City's press release (PDF) regarding backflow prevention).

Please note that any new backflow installations or replacements are required to pull a permit through the Permit Center of the City's Planning and Development Services Department. Please see their webpage for more information on permitting. 


  1. What is a cross-connection?
  2. What is backflow?
  3. What is backpressure backflow?
  4. What is back-siphonage?
  5. Why does the Water / Wastewater Utilities Department need to control cross-connections and protect its public water system against backflow?
  6. What should a water supplier do to control cross-connections and protect their public water systems against backflow?
  7. What is a backflow preventer?
  8. What is an air gap?
  9. What is a reduced pressure zone assembly?
  10. What is a double-check valve assembly?
  11. What is a hose bibb vacuum breaker?
  12. Where can I get more information about cross-connection control?
  13. Why do backflow preventers have to be tested periodically ?
  14. Why does a soft drink dispensing machine require backflow protection?
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