Presentation on theme: "September 29-30, 2011 Drinking Water Program Sustained Compliance Workshop Lee Johnson, P.E. 907-451-2179."— Presentation transcript:
September 29-30, 2011 Drinking Water Program Sustained Compliance Workshop Lee Johnson, P.E
Objectives What is a Cross Connection? How are they regulated? What is a Back Flow Preventer? Types of Preventers Examples of Cross Connections
What is a Cross Connection? Defined in 18 AAC (a)(36) Basically it is an ACTUAL or POTENTIAL physical connection or arrangement between otherwise separate piping systems containing potable water and any contaminant, whereby water may flow between the two systems.
Back Pressure: Pressure of nonpotable fluid is greater than pressure of potable water. Back Siphonage: Negative pressure in potable water piping causes nonpotable fluid to be siphoned into potable water line.
High or Low Hazard Low Hazard - will not have an immediate effect on health, but could have an impact on the potable water. High Hazard - will cause an immediate toxic effect or cause immediate and severe illness.
Cross Connections Are Prohibited 18 AAC (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 (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 (b).
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.
Statutes & Codes Alaska Statutes: Article 8 Section Portions of Uniform Plumbing Code – 2009 adopted by reference, 18 AAC (c) UPC Chapter 6 Section 603 pertains to Cross Connections Table 6-2 Backflow Prevention Devices, Assemblies, and Methods
Service Connections and Premise Plumbing Drinking water program regulates water systems – Sources, treatment, and distribution systems, not service connections. There is risk within a building from cross connections even if distribution system is protected. Plumbing Code What about cross connections within your facility? Need to protect potable taps from nonpotable use taps within water plant.
Plan Review & Sanitary Survey During engineering plan reviews we look for Cross Connections within the public water system, the treatment plant, and the water distribution system. BUT…….. For existing systems the sanitary survey process is the only other opportunity for staff or inspectors to look for and ask questions about facilities connected to the distribution system? Also – Systems and plants are often modified through routine maintenance resulting in new cross connections or elimination of backflow prevention.
Owners, Operators, and Surveyors Should Consider: Types of facilities connected to drinking water distribution system (Actual or Potential Hazards?): Health Clinics Hospitals Schools Water and Wastewater Treatment plants Mortuaries Other
Others? What other potential or actual cross connections can you name?
Direct vs Indirect
Devices and Assemblies Device -- cannot be tested Assembly -- has two isolation valves and has test cocks for proper testing of the backflow prevention assembly
Backflow Prevention Air Gap 2 Pipe Diameters or 1 inch minimum RPZ Reduced Pressure Zone Assembly DC Double Check Valve Assembly PVB Pressure Vacuum Breaker AVB Atmospheric Vacuum Breaker
Backflow Prevention Prevents Backsiphonage LOW & HIGH HAZARD Proper Air Gap Atmospheric Vacuum Breaker Pressure Vacuum Breaker Reduced Pressure Zone BFP Double Check Valve (low hazard only) Prevents Backpressure LOW HAZARD Proper Air Gap Double Check Valve HIGH HAZARD Proper Air Gap Reduced Pressure Zone BFP
Insert New table 6-2
Air Gap Flow condition Non flow condition Atmospheric Vacuum Breaker Protection
EXAMPLE AIR GAPS
Tank Air Gap POTABLE SUPPLY PUMP FLOAT NONPOTABLE APPLICATION
Hose Bibb Vacuum Breaker
Pressure Vacuum Breaker TEST PORTS NORMAL FLOW
Double Check Valve
FLOW DIRECTION #1 GATE VALVE #2 CHECK VALVE Reduced Pressure Zone Backflow Prevention Assembly (RPZ) TEST PORTS PRESSURE DIFFERENTIAL RELIEF VALVE #2 CHECK VALVE #1 CHECK VALVE #2 GATE VALVE High hazard condition
RPZ – Proper Installation?
Pumping Station Cross-connections 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. GATE VALVE FLOOR DRAIN AIR VACUUM RELEASE SILENT CHECK
Treatment Bypass Piping
Emergency Bypass Installed
Filter Bypass Piping Bypass Piping
Disinfection Bypass Piping
Water Meter as Cross Connection?
Surface Wash Arms
Surface Wash Arm – Pressure Filter
Backwash Waste Lines
Softener Backwash Waste Line
UV and Cross Connections?
Treatment Plant Lab Sink
Distribution System Direct connections to sewers for flushing either the water main or sewer.
Alaska Drinking Water Regulations 18AAC American Water Works Association Recommended Practice for Backflow Prevention and Cross Connection Control – M14 EPA’s Cross Connection Control Manual Uniform Plumbing Code Chapter 6 Kenneth Kerry Water Distribution System O&M Manual USC Foundation for Cross-Connection Control and Hydraulic Research Lots of internet resources