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Sponsored by
Randy Holland
Premise Isolation Backflow Prevention:
Best Practices & Standard Details Part 1
Presented by
Part 3: The Differences Between DC & RPZ Backflow
Preventers
Premise Isolation Backflow Prevention:
Best Practices & Stand...
Premise Isolation: Best Practices & Standard Details
….Definitions and term use:
Isolation backflow prevention: In additio...
….Definitions and term use:
Containment or ‘Premise Isolation’ backflow prevention: For public water systems, water that
h...
Introduction
The water engineering community has been struggling with new
professional liability risk involving the locati...
Introduction
Can we rid ourselves of the
problem by dumping the
system itself?
Sadly, we are learning
through SCADA and AM...
Introduction
With this new risk realization comes a new interested party: The insurance
company. Because of this very publ...
Assuming the legal rights of a person for whom expenses or a debt has been paid.
Typically, an insurance company which pay...
Introduction
…Meanwhile, at the 2016-17 bi-annual conference of the American Society
of Plumbing Engineers, one popular le...
Introduction
According to a survey of 1220 U.S. civil
and plumbing engineers conducted
over a 19‐month period, 3 out of 4 ...
• Water Districts NEED
Premise Isolation in
order to fulfill their EPA
mandate; and
Introduction
Bottom Line:
“…. The retu...
1. Water utilities are seeking more
premise-isolation.
2. That more containment systems are
being specified as RPZ regardl...
2 types of backflow Preventers:DesigndifferencesDCvs.RPZ
Double-Check Valve
Assemble, DC or
DCDA
Reduced Pressure Zone
Val...
2 types of backflow Preventers:DesigndifferencesDCvs.RPZ
Double-Check Valve
Assemble, DC or
DCDA
Reduced Pressure Zone
Val...
DC: Low hazard?
Public
(Supply)
side
Property
(Private)
side
Flow
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
...
DC: Low hazard?DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
But no remedy exists in the event of a malfunction ...
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
RPZ: Fail-safe against returning water
Flow
Property
(Private)
sid...
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
RPZ: Fail-safe against returning water
Flow
Property
(Private)
sid...
Flow Stop
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
RPZ: Fail-safe against returning water
In a flow-stop si...
Loss of pressure
#2
valve
blocked
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
Consider a flow-stop situation, ...
#1
valve
Failure
Normal
delivery
pressure
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
Now consider a failure o...
#1
valve
Failure
Blockag
e relief
valve
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
RPZ: Fail-safe against ret...
DesigndifferencesDCvs.RPZ
Design Differences DC vs. RPZ
No
demand
Normal
delivery
pressure
RPZ: Fail-safe against returnin...
DesigndifferencesDCvs.RPZ
Double-Check Valve
Assemble, DC or
DCDA
Reduced Pressure Zone
Valve Assembly, RP
RPDA
Safe-T-Cov...
 The public water supply is unprotected from returning water without a
premise isolation system. RPZs are only fail-safe ...
 Safe-T-Cover's blog: Updated weekly with articles on backflow prevention,
standard details, and best practices.
 Enclos...
Thank You!
Premise Isolation: Best Practices & Standard Details
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Backflow Best Practices and Standard Details: Part 1

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This presentation focuses on the differences between DC and RPZ backflow preventers.

This is the first of a three part series on backflow preventer installation, standard details, and best practices. The series focuses on three key facts: Water utilities are seeking more premise-isolation cross connection control. More containment systems are being specified as RPZ regardless of hazard threshold. The AWWA, ASPE, & the legal community recognize “outside aboveground” as ‘best practice’ for backflow installation.

Part 2: http://www.slideshare.net/CraigCarmon/backflow-best-practices-and-standard-details-part-2
Part 3: http://www.slideshare.net/CraigCarmon/backflow-best-practices-and-standard-details-part-3

Published in: Engineering
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Backflow Best Practices and Standard Details: Part 1

  1. 1. Sponsored by Randy Holland Premise Isolation Backflow Prevention: Best Practices & Standard Details Part 1 Presented by
  2. 2. Part 3: The Differences Between DC & RPZ Backflow Preventers Premise Isolation Backflow Prevention: Best Practices & Standard Details
  3. 3. Premise Isolation: Best Practices & Standard Details ….Definitions and term use: Isolation backflow prevention: In addition to the lavatory and water fountain, most buildings’ plumbing systems include fixtures that are designed to clean contaminated equipment, carbonate beverages, and even infuse chemicals and detergents. Many of these processes create dangerous and toxic substances. If these substances were allowed to reverse back into the building’s fresh water piping, an event known as backflow, it would create serious health hazards for the individuals on site. Building authorities deal with these risks by specifying appropriate backflow preventer assemblies at those specific locations where contamination is a risk. The term for this solution is “isolation backflow prevention” because a special plumbing apparatus known as a backflow preventer isolates high-hazard fixtures and equipment at the point of use from the rest of the on-site piping system.
  4. 4. ….Definitions and term use: Containment or ‘Premise Isolation’ backflow prevention: For public water systems, water that has been delivered through its water meter to a water customer is only done safely and responsibly when there is no possibility that that water will return back from the customer to the water system, an event (also) known as backflow. Disparate groups within plumbing, design, and water management have devised their own favorite terms for this system. The plumbing community prefers “Containment backflow prevention” because such systems contain delivered water at the subscriber’s premises; On the other hand, water districts tend to prefer “Premise Isolation”. It is important to understand that whether called Containment or Premise Isolation, we are referring to the task of eliminating backflow at the Point of Supply from the public water system. This presentation is limited to the recognized best practices of these containment or premise isolation systems. Premise Isolation: Best Practices & Standard Details
  5. 5. Introduction The water engineering community has been struggling with new professional liability risk involving the location of premise isolation backflow preventer systems; Not because of new design practices, but because of new information about the old practices. There has been a slow trickle of warnings for years, but in the past 3 years important organizations and industry leaders have added new warnings with much stronger language that not only change recognized best practices, but actually challenge the fitness and safety of older placement methods altogether. Premise Isolation: Best Practices & Standard Details
  6. 6. Introduction Can we rid ourselves of the problem by dumping the system itself? Sadly, we are learning through SCADA and AMI that there is actually more backflow occurring at the premise than we previously suspected. Premise Isolation: Best Practices & Standard Details
  7. 7. Introduction With this new risk realization comes a new interested party: The insurance company. Because of this very public commentary from experts and leading groups, casualty carriers, through subrogation, have new weapons for damage recovery. And anytime the accused designer is able to demonstrate that local government contributed, whether materially or passively, to the poor design, the water district and/or building authority may be at risk for the liability. Premise Isolation: Best Practices & Standard Details
  8. 8. Assuming the legal rights of a person for whom expenses or a debt has been paid. Typically, an insurance company which pays its insured client for injuries and losses then sues the party which the injured person contends caused the damages to him/her. Introduction Because of subrogation, the water district needs to demonstrate that no unsafe methods are promoted by their plans review teams. The best way to demonstrate that is with published standard details and drawings that are consistent with recognized best practices. Premise Isolation: Best Practices & Standard Details
  9. 9. Introduction …Meanwhile, at the 2016-17 bi-annual conference of the American Society of Plumbing Engineers, one popular learning module titled “Let the Civil Engineer Deal with the Containment Backflow System” suggests that leadership is seeking reassignment of the premise isolation backflow system design to the civil discipline. No surprise, other than how long it took to realize… Plumbing engineers have nothing to gain and everything to lose when they specify indoor RPZs because • The flood risks now being realized from indoor installations of RPZs is extraordinary; • Designing for outdoor placement includes grading and surface contouring for sudden flood water flows; a task that is beyond the scope of a plumbing engineer’s training or expertise. Premise Isolation: Best Practices & Standard Details
  10. 10. Introduction According to a survey of 1220 U.S. civil and plumbing engineers conducted over a 19‐month period, 3 out of 4 say they need local water authorities to provide standard details for outdoor aboveground backflow preventer systems. You can read more about the results of this survey here. Premise Isolation: Best Practices & Standard Details
  11. 11. • Water Districts NEED Premise Isolation in order to fulfill their EPA mandate; and Introduction Bottom Line: “…. The return of any water to the public water system after the water has been used for any purpose on the customer’s premises or within the customer’s piping system is unacceptable and opposed by AWWA.…” • Premise-Isolation design details and specifications need to be provided to civil engineers because of their general familiarity with standard details and their comparable lack of familiarity with backflow systems. AWWA’s preamble to the Cross Connection Control Manual, published by EPA Premise Isolation: Best Practices & Standard Details
  12. 12. 1. Water utilities are seeking more premise-isolation. 2. That more containment systems are being specified as RPZ regardless of hazard threshold. 3. AWWA, ASPE, & the legal community recognize “outside aboveground” as ‘best practice’ for premise isolation. This presentation will show… Introduction Premise Isolation: Best Practices & Standard Details
  13. 13. 2 types of backflow Preventers:DesigndifferencesDCvs.RPZ Double-Check Valve Assemble, DC or DCDA Reduced Pressure Zone Valve Assembly, RP RPDA A designer may specify one of two types of BFPs for premise isolation. Up until recently, the decision for which assembly to specify was based solely on the perceived hazard to the waste water system created by the processes of the end user. High hazard (better named, high waste-hazard) uses were required to utilize an RPZ. Uses that did not pose a risk to the waste water were allowed to use a DC. Design Differences DC vs. RPZ Premise Isolation: Best Practices & Standard Details
  14. 14. 2 types of backflow Preventers:DesigndifferencesDCvs.RPZ Double-Check Valve Assemble, DC or DCDA Reduced Pressure Zone Valve Assembly, RP RPDA Design Differences DC vs. RPZ For example, a medical facility or a chemical plant triggered the requirement for an RPZ while an office or simple retail user would be allowed to use a DC or, depending on the municipality, no premise isolation system at all. Now, as we will discuss below, many purveyors are requiring RPZs on all premise isolation systems because of the inherent limits of protection provided by the double check valve for the public water supply. Premise Isolation: Best Practices & Standard Details
  15. 15. DC: Low hazard? Public (Supply) side Property (Private) side Flow DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ The Double-check assembly was developed in the 1950s for the fire industry. And for many years it was regarded as a satisfactory solution. The design is simple. Any time system-water pressure on the property (private) side exceeds the system pressure on the city (public) side, two redundant check valves close and water stops flowing backwards. Premise Isolation: Best Practices & Standard Details
  16. 16. DC: Low hazard?DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ But no remedy exists in the event of a malfunction of the valve closures or if debris in the water line causes the valves to not close completely. Additionally, the DC is a closed, or blind system making detection of any failure impossible without a field test performed by a licensed tester. Today, millions of DCs are in service that may have failed. When a Florida city began its annual testing program in 2010, it found 52% of the valves in service had failed with no way to determine how long they had been inoperable. Public (Supply) side Property (Private) side Flow Premise Isolation: Best Practices & Standard Details
  17. 17. DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ RPZ: Fail-safe against returning water Flow Property (Private) side Public (Supply) side The RPZ emerged in the 1970s as a remedy to the double-check limitations. Like the DC, it incorporates 2 redundant check valves. But unlike the DC, the RPZ incorporates a hydraulically operated differential relief valve directly beneath the # 1 check valve. It is this relief valve’s placement (along with the universal laws of hydraulics) that make this a fail-safe solution for water purveyors. As elegant as the design is, it comes at a cost. And that cost is the surrounding area. Premise Isolation: Best Practices & Standard Details
  18. 18. DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ RPZ: Fail-safe against returning water Flow Property (Private) side Public (Supply) side As the DC reveals, valves fail. But when they fail in an RPZ, the assembly is designed to create a deluge event directly under the assembly so that no contaminated water returns to the public water supply. Because of the danger of contamination, no water from the relief valve may be piped directly from the assembly. It must release into the atmosphere away from any piping. Watch this short video revealing an actual discharge. Premise Isolation: Best Practices & Standard Details
  19. 19. Flow Stop DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ RPZ: Fail-safe against returning water In a flow-stop situation the water between the check valves will often drain out the relief valve. Some think that that event defines the limit of what water can ever flow into a drain. Not so. Premise Isolation: Best Practices & Standard Details
  20. 20. Loss of pressure #2 valve blocked DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ Consider a flow-stop situation, one that might naturally occur at the end of the day. If you look closely, you can see that a small pebble has lodged in the #2 check valve. Now let’s say there’s a fire around the corner that causes back siphon at this point in the system. Because the # 2 check valve is not closing, all the water that has been delivered to the building will continue to flow out the relief valve until the private lines are cleared. If this is a four story building, that’s a lot of water! RPZ: Fail-safe against returning water Premise Isolation: Best Practices & Standard Details
  21. 21. #1 valve Failure Normal delivery pressure DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ Now consider a failure of the #1 check valve. Under normal operating conditions, this failure would go unnoticed. After all, water is being called for by the user through the opening of taps. The water flows in undeterred. But with this imbalance in the system, changes in demand tend to rock the remaining valves open and closed sporadically. RPZ: Fail-safe against returning water Demand Premise Isolation: Best Practices & Standard Details
  22. 22. #1 valve Failure Blockag e relief valve DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ RPZ: Fail-safe against returning water Demand Normal delivery pressure This creates the conditions for the “perfect storm” scenario. The imbalance created by the # 1 failure makes the relief valve more prone to opening momentarily, allowing debris to block the closure of that valve. Under such conditions, a constant flow of delivered water will begin to flow directly out the relief valve. This reduces water pressure for the user, but delivery will continue. Premise Isolation: Best Practices & Standard Details
  23. 23. DesigndifferencesDCvs.RPZ Design Differences DC vs. RPZ No demand Normal delivery pressure RPZ: Fail-safe against returning water The real damage begins when the user stops using water such as at the end of a work day. With the relief valve blocked open and the # 1 valve inoperative, all the water that the purveyor can provide will flow unabated out the relief valve wherever it might be, and continue until the water source is interrupted. This is the scenario that must be avoided: the perfect storm. Premise Isolation: Best Practices & Standard Details
  24. 24. DesigndifferencesDCvs.RPZ Double-Check Valve Assemble, DC or DCDA Reduced Pressure Zone Valve Assembly, RP RPDA Safe-T-Cover has put together an easy to reference guide on the differences between double checks and reduced pressure zone backflow preventers on their blog. Design Differences DC vs. RPZ Premise Isolation: Best Practices & Standard Details
  25. 25.  The public water supply is unprotected from returning water without a premise isolation system. RPZs are only fail-safe solution.  The duties of the building/plumbing authority and the plumbing code do not wholly satisfy the duties of the water utility.  Indoor RPZs 3” and larger are perpetual floods risks.  The need to address sudden on-site water flows disqualify MEPs from outdoor premise isolation design, even if within MEP halo.  Civil engineers are unfamiliar with BPA installations and need standard details from water authorities. Take-Aways  A broadly adopted region-wide set of guidelines would save cities 100s of hours in plans-review time. Premise Isolation: Best Practices & Standard Details
  26. 26.  Safe-T-Cover's blog: Updated weekly with articles on backflow prevention, standard details, and best practices.  Enclosure Design eBook: Learn the 5 design considerations for aboveground enclosures  Recent story on decision to add standard details by the city of Arlington, Texas  Trends in Backflow Preventer Installation: A downloadable guide to the latest trends in backflow best practices. Additional Resources Premise Isolation: Best Practices & Standard Details
  27. 27. Thank You! Premise Isolation: Best Practices & Standard Details

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