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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?.

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Backflow training

Backflow Training

Introduction to Backflow

For Irrigation Systems


Agenda
Agenda

  • Backflow definitions

  • Hydraulics

  • Degree of Hazard

  • Types of Backflow Preventers

  • Product Selection

  • Approvals

  • Installations


What is backflow
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
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 connection1
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
Hydraulics

  • Back-pressure

  • Back-siphonage

  • Head

  • Barometric loop

  • Continuous vs. non-continuous pressure


Back 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
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
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
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

Degree of Hazard


Types of backflow preventers used in irrigation systems
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
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
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
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

AVB



Anti siphon valves
Anti-Siphon Valves

  • Non-Testable

  • Not USC Approved

  • Usually not inspected


Pressure vacuum breaker pvb
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
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.

PVB




Double check valve assembly dc
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
Double Check Valve Assembly

  • Protects against a non-health hazard.

  • Back-pressure condition.

  • Back-siphonage condition.

  • Continuous pressure applications.

DC




Reduced pressure principal backflow preventer rp
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
Reduced Pressure Principal Backflow Preventer

  • Protects against a health hazard.

  • Back-pressure condition.

  • Back-siphonage condition.

  • Continuous pressure applications.

  • The Ultimate in mechanical protection.

RP

Rules









Troubleshooting an rp assembly
Troubleshooting an RP Assembly

  • Turn off number 2 shutoff valve

  • If discharge stops, problem is in 2nd Check


Troubleshooting an rp assembly1
Troubleshooting an RP Assembly

  • If discharge continues, induce flow by opening number four testcock

  • If discharge stops or slows dramatically, problem is in first check


Troubleshooting an rp assembly2
Troubleshooting an RP Assembly

  • If discharge continues with no change, problem is in relief valve



Specify the proper device for the application
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

FCCC&[email protected]

FM

Listings

ASSE

UPC

UL

CSA

AWWA (Voluntary Standard - Certified to)

Approvals and Listings


Installation requirements
Installation Requirements

  • Hydraulics

  • Accessibility for testing and repair

  • Indoor vs. Outdoor

  • Freeze protection

  • Vandal protection

  • Relief valve discharge



Double check assembly installations

Below Grade

Above Grade

Double Check Assembly Installations



Irrigation systems issues
Irrigation Systems Issues

  • Quick closing solenoid valves

    • Create water hammer

    • Cause RP to discharge

      • Soft seated check valve between solenoid and RP

    • Cause noise

      • Install water hammer arrestor


Water hammer devices

Soft Seated Check

Water Hammer Arrestor

Water Hammer Devices


Key terms

Accessible

Approved Assembly

Approved Check Valve

Isolation

Backflow program

Administrative Authority

Annual test

Certified Tester

Containment

Point of use

Key Terms



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