Backflow Training Introduction to Backflow For Irrigation Systems

Agenda n n n n Backflow definitions Hydraulics Degree of Hazard Types of Backflow Preventers Product Selection Approvals Installations

What is Backflow? n 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.

Normal Flow

What is a Cross Connection? n 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? n A direct cross connection is subject to both back-siphonage and back-pressure. n n Usually a hard piped connection An in-direct cross connection is subject to back-siphonage only. n Can be a potential cross connection

Hydraulics n n n Back-pressure Back-siphonage Head Barometric loop Continuous vs. non-continuous pressure

Back-Pressure n n 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 n n Change in elevation of the downstream piping. High pressure piping interconnect

Back-Pressure

Back-Siphonage n n 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 n n n Undersize piping Line breaks High water withdrawal rates

Back-Siphonage

Head n n 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 n n n 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 n Non-continuous n n System cannot realize more than 12 hours of continuous pressure per 24 hour period. Continuous n Anything that is not non-continuous!

Degree of Hazard n Low Hazard n High Hazard n Non-Health Hazard n Pollution n Contamination

Types of Backflow Preventers used in Irrigation Systems n n Atmospheric Vacuum Breaker Pressure Vacuum Breaker Double Check Assembly Reduced Pressure Principal Assembly

Types of Non-Mechanical Backflow Preventers n Air Gap n n n 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.

Air-Gap

Atmospheric Vacuum Breaker n n n 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. . . n n 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) n n n Protects against a health hazard Back-siphonage condition only. Non-continuous pressure application. n No more than 12 hours of pressure per 24 hour period

Atmospheric Vacuum Breaker

Anti-Siphon Valves n n n Non-Testable Not USC Approved Usually not inspected

Pressure Vacuum Breaker (PVB) n Contains. . . n n 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 n n n Protects against a health hazard. Back-siphonage condition only. Continuous pressure application. n Can realize pressure for 12 hours or more per 24 hour period.

Pressure Vacuum Breaker

Double Check Valve Assembly (DC) n n n Contains two independently-acting approved check valves. Four resilient-seated test cocks. Two resilient-seated isolation valves.

Double Check Valve Assembly n n 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) n n 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 n Protects against a health hazard. Back-pressure condition. Back-siphonage condition. Continuous pressure applications. n The Ultimate in mechanical protection. n n n

Reduced Pressure Assembly - Small

Reduced Pressure Assembly Large

Operation of an RP Device

No-Flow Condition

Normal Flow

Backpressure with 2 nd Check Fouled

Backsiphonage with 2 nd Check Fouled

Troubleshooting an RP Assembly 1. 2. Turn off number 2 shutoff valve If discharge stops, problem is in 2 nd Check

Troubleshooting an RP Assembly 3. 4. If discharge continues, induce flow by opening number four testcock 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 n n 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 n Approvals n n FCCC&HR@USC FM n Listings n n n ASSE UPC UL CSA AWWA (Voluntary Standard - Certified to)

Installation Requirements n n n Hydraulics Accessibility for testing and repair Indoor vs. Outdoor Freeze protection Vandal protection Relief valve discharge

Pressure Vacuum Breaker Installations

Double Check Assembly Installations n Below Grade n Above Grade

RP Assembly Installations

Irrigation Systems Issues n Quick closing solenoid valves n n Create water hammer Cause RP to discharge n n Soft seated check valve between solenoid and RP Cause noise n Install water hammer arrestor

Water Hammer Devices n Soft Seated Check n Water Hammer Arrestor

Key Terms n n n Accessible Approved Assembly Approved Check Valve Isolation Backflow program n n n Administrative Authority Annual test Certified Tester Containment Point of use

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