Cross Connections. September 29-30, 2011 Drinking Water Program Sustained Compliance Workshop Lee Johnson, P.E. [email protected] 907-451-2179. Objectives. What is a Cross Connection? How are they regulated? What is a Back Flow Preventer? Types of Preventers
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September 29-30, 2011
Drinking Water Program
Sustained Compliance Workshop
Lee Johnson, P.E.
Backflow – TwoTypes
Pressure of nonpotable fluid is greater than pressure of potable water.
Negative pressure in potable water piping causes nonpotable fluid to be siphoned into potable water line.
18 AAC 80.025(a)
A person may not construct, install, or use a cross connection in a public water system, or allow a water system that contains a cross-connection to connect to a public water system.
18 AAC 80.025(b)
If the department determines that a facility has the potential to contaminate public water system through backflow, the owner or operator of the public water system shall install, maintain, and test on the service line to and at other locations in that facility, a backflow prevention device that conforms to ANSI/AWWA Standards C510-97, Double Check Valve Backflow prevention Assembly, or C511-97, Reduced-Pressure Principle Backflow Prevention Assembly, adopted by reference in 18 AAC 80.010(b).
18 AAC 80.025(b) continued
The owner or operator of the public water system may delegate the installation, maintenance, and testing of the backflow prevention device to the owner or operator of the facility that poses the risk. This delegation does not relieve the owner or operator of the public water system of the responsibility to install, maintain, and test the backflow prevention device.
Types of facilities connected to drinking water
distribution system (Actual or Potential Hazards?):
2 Pipe Diameters or 1 inch minimum
LOW & HIGH HAZARD
Non flow condition
Atmospheric Vacuum Breaker
EXAMPLE AIR GAPS
Hose Bibb Vacuum Breaker
Pressure Vacuum Breaker
Double Check Valve
Reduced Pressure Zone Backflow Prevention Assembly (RPZ)
#2 CHECK VALVE
#1 CHECK VALVE
#1 GATE VALVE
#2 GATE VALVE
#2 CHECK VALVE
High hazard condition
Priming of raw water pumps with finished water.
Air relief valves piped directly to a drain.
•Cooling water for an emergency generator submerged in a drain or returned to the potable supply.
Pumping Station Cross-connections
AIR VACUUM RELEASE
• Direct connections to sewers for flushing either the water main or sewer.
Alaska Drinking Water Regulations
American Water Works Association
Recommended Practice for Backflow Prevention and Cross Connection Control – M14
EPA’s Cross Connection Control Manual
Uniform Plumbing Code
Water Distribution System O&M Manual
USC Foundation for Cross-Connection Control and Hydraulic Research
Lots of internet resources