Presentation on theme: "Backflow Training Introduction to Backflow For Irrigation Systems."— Presentation transcript:
Backflow Training Introduction to Backflow For Irrigation Systems
Agenda Backflow definitions Hydraulics Degree of Hazard Types of Backflow Preventers Product Selection Approvals Installations
What is Backflow? The undesirable reversal of flow of water or mixtures of water and other liquids, gases, or other substances into the potable water supply from any source or sources.
What is a Cross Connection? Any unprotected actual or potential connection between a public or a consumer’s potable water system and any other source or system through which it is possible to introduce into any part of the potable water system any used water, industrial fluid, gas, or substance other than the intended potable water with which the system is supplied.
What is a Cross Connection? A direct cross connection is subject to both back-siphonage and back-pressure. Usually a hard piped connection An in-direct cross connection is subject to back-siphonage only. Can be a potential cross connection
Hydraulics Back-pressure Back-siphonage Head Barometric loop Continuous vs. non-continuous pressure
Back-Pressure Any elevation of pressure in the downstream piping system above the supply pressure at the point of consideration which would cause a reversal of the normal direction of flow. Causes Change in elevation of the downstream piping. High pressure piping interconnect
Back-Siphonage Any decrease of pressure that causes a negative or sub-atmospheric pressure to exist in the upstream piping ahead of the point of consideration which would cause a reversal of the normal direction of flow. Causes Undersize piping Line breaks High water withdrawal rates
Head The term “head” is used to describe pressure. One foot of head equals.433 pounds per square inch. In the backflow industry, the pressure loss through the valve is called “head loss”. All manufacturers express the head loss of their valves in units of pounds per square inch.
Head 27 3/4” of water generates a pressure of one pound per square inch (psi) 27 3/4” 1 psi
Barometric Loop A barometric loop is a horseshoe-shaped loop in a water line, that has a height greater than 33.9 ft. A very effective means of preventing backflow due to back-siphonage. Impractical due to physical size.
Pressure Non-continuous System cannot realize more than 12 hours of continuous pressure per 24 hour period. Continuous Anything that is not non-continuous!
Degree of Hazard Low Hazard Non-Health Hazard Pollution High Hazard Health Hazard Contamination
Types of Backflow Preventers used in Irrigation Systems Atmospheric Vacuum Breaker Pressure Vacuum Breaker Double Check Assembly Reduced Pressure Principal Assembly
Types of Non-Mechanical Backflow Preventers Air Gap A physical separation between the free flowing discharge end of a potable water supply pipeline and an open or non-pressure receiving vessel. An “approved air gap” shall be at least double the diameter of the supply pipe measured vertically above the overflow rim of the vessel. Never less than 1 inch.
Atmospheric Vacuum Breaker Contains a float-check, a check seat, and an air inlet port. Water flow causes the float to close the air inlet port. When the flow of water stops... The float falls and forms a check valve against back-siphonage The air inlet port opens to allow air to enter and satisfy the vacuum.
Atmospheric Vacuum Breaker (AVB) Protects against a health hazard Back-siphonage condition only. Non-continuous pressure application. No more than 12 hours of pressure per 24 hour period
Atmospheric Vacuum Breaker
Anti-Siphon Valves Non-Testable Not USC Approved Usually not inspected
Pressure Vacuum Breaker (PVB) Contains... Independently-acting, internally-loaded check valve. Independently-acting, loaded air inlet valve located on the discharge side of the check valve. Two resilient-seated test cocks. Two resilient-seated isolation valves.
Pressure Vacuum Breaker Protects against a health hazard. Back-siphonage condition only. Continuous pressure application. Can realize pressure for 12 hours or more per 24 hour period.
Pressure Vacuum Breaker
Double Check Valve Assembly (DC) Contains two independently-acting approved check valves. Four resilient-seated test cocks. Two resilient-seated isolation valves.
Double Check Valve Assembly Protects against a non-health hazard. Back-pressure condition. Back-siphonage condition. Continuous pressure applications.
Double Check Assembly - Small
Double Check Assembly - Large
Reduced Pressure Principal Backflow Preventer (RP) Contains two independently-acting approved check valves. A hydraulically-operating, mechanically independent differential pressure relief valve located between the two check valves. Four resilient-seated test cocks. Two resilient-seated isolation valves.
Reduced Pressure Principal Backflow Preventer Protects against a health hazard. Back-pressure condition. Back-siphonage condition. Continuous pressure applications. The Ultimate in mechanical protection.
Reduced Pressure Assembly - Small
Reduced Pressure Assembly - Large
Operation of an RP Device
Backpressure with 2nd Check Fouled
Backsiphonage with 2nd Check Fouled
Troubleshooting an RP Assembly 1. Turn off number 2 shutoff valve 2. If discharge stops, problem is in 2 nd Check
Troubleshooting an RP Assembly 3. If discharge continues, induce flow by opening number four testcock 4. If discharge stops or slows dramatically, problem is in first check
Troubleshooting an RP Assembly 5. If discharge continues with no change, problem is in relief valve
Product Selection Guide
Specify the Proper Device for the Application We can communicate industry standards for degree of hazard, hydraulic and backflow conditions. Up to authority having jurisdiction to make the final decision.
Approvals and Listings Approvals FM Listings ASSE UPC UL CSA AWWA (Voluntary Standard - Certified to)
Installation Requirements Hydraulics Accessibility for testing and repair Indoor vs. Outdoor Freeze protection Vandal protection Relief valve discharge