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Backflow Prevention: Let the Civil Engineer Deal With It

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Plumbing engineers are facing new liability risks from insurance carriers, revealed by new warnings and commentary from industry leadership regarding indoor containment RPZs. Because of the need for pure water in the public water supply and the undetectable nature of the DCs, purveyors are demanding more RPZs and ignoring the legacy hazard guidance. RPZs are designed to engulf the immediate surrounding area. Indoor placement of 3” & larger RPZs adds irrational risk for PO & designer. Placing the CBPA inside costs PO $000s more than outside. There is a need to address sudden flood water flows disqualifies MEP from CBPA Design. Your local water district must be encouraged to adopt new details and guidelines that promote best practices and adoption by CEs.

Published in: Engineering
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Backflow Prevention: Let the Civil Engineer Deal With It

  1. 1. Presentation to the 2016 ASPE Convention & Expo Let the Civil Designer Deal with the Containment Backflow Preventers 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.
  2. 2. • Water Districts NEED Containment in order to fulfill their EPA mandate; and 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.…” • Containment 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 Introduction
  3. 3. 1. Design differences DC vs. RPZ; Why it matters 2. Current placement practices 3. The real flood risks of indoor RPZs 4. The real cost of indoor containment 5. The explosive growth of the RPZ and how it impacts M/P Engineers 6. How do we encourage transitioning this task to the civil engineering discipline? Today We’ll Cover… Let the Civil Designer Deal with the Backflow System
  4. 4. 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. 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. 1. Design Differences (and why it matters)
  5. 5. DC: Low hazard? Public (Supply) side Property (Private) side Flow DesigndifferencesDCvs.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. 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. 1. Design Differences (and why it matters)
  6. 6. DesigndifferencesDCvs.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. 1. Design Differences (and why it matters) 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.
  7. 7. Flow Stop DesigndifferencesDCvs.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. 1. Design Differences (and why it matters)
  8. 8. Loss of pressure #2 valve blocked #2 valve blocked DesigndifferencesDCvs.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 1. Design Differences (and why it matters) #2 Valve blocked
  9. 9. #1 valve Failure #1 valve Failure Normal delivery pressure DesigndifferencesDCvs.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 1. Design Differences (and why it matters) #1 Valve failure
  10. 10. #1 valve Failure #1 valve Failure Blockage relief valve Blockage relief valve DesigndifferencesDCvs.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. 1. Design Differences (and why it matters) Blockage Relief Valve #1 Valve failure
  11. 11. DesigndifferencesDCvs.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. 1. Design Differences (and why it matters)
  12. 12.  Above ground in an enclosure  Inside a building  Inside a vault – Click here for more 3 options for backflow preventer placement 2. Placement Practices
  13. 13.  Inside a building  Above ground in an enclosure – Click here for more  Inside a vault 3 options for backflow preventer placement 2. Placement Practices
  14. 14.  Inside a building  Above ground in an enclosure  Inside a vault 3 options for backflow preventer placement 2. Placement Practices
  15. 15.  Inside a building 3 options for backflow preventer placement 1. Professional liability: indoor flooding Here’s what the American Society of Plumbing Engineers advise about indoor RPZs. “Before an RPZ is located, consideration should be given to both how much water will be discharged, and where it will drain. Consideration must be given to the drain system to assure the drainage system can handle the load. If a drain is not capable of accepting the flow, other choices as to the location of the valve, such as outside in a heated enclosure, should be made.” -2006 ASPE Plumbing Engineering Design Handbook, vol 2, p 70 3. The Real Flood Risks of indoor RPZs
  16. 16.  Inside a building 3. The Real Flood Risks of indoor RPZs 3 options for backflow preventer placement This flood occurred in a hospital mechanical room causing over $1M in damage. You are looking at two sides of one wall. 1. Professional liability: indoor flooding
  17. 17.  Inside a building 3 options for backflow preventer placement On the left, we see that the sudden water flow and volume moved the wall into the next room (right photo), which happened to be a telephone and low-voltage wiring room. 1. Professional liability: indoor flooding 3. The Real Flood Risks of indoor RPZs
  18. 18.  Inside a building 3 options for backflow preventer placement The insurer sought recovery from all the risk holders including the engineer, architect, contractor, subcontractor, and even the most recent recorded tester; While the details of who paid what were not made public, we do know that the property insurer was made whole by one or more of the listed defendants. 1. Professional liability: indoor flooding 3. The Real Flood Risks of indoor RPZs
  19. 19.  Inside a building 3 options for backflow preventer placement In times past, this event would have been seen as an unforeseeable casualty, a pipe burst. But insurers have been listening to the next part of the discussion. This commentary from experts changed everything. 1. Professional liability: indoor flooding 3. The Real Flood Risks of indoor RPZs
  20. 20.  Inside a building 3 options for backflow preventer placement So if an RPZ is designed to dump water, then drain capacity is the issue. The chart on the right is from the manufacturer of the BPA seen in the previous flood photos. It illustrates the anticipated flow rate from the relief valve at various pipe sizes and at various pressures. Note that the assembly shown will flow 375 GPM at 85 PSI. A 4” drain pipe with a 1% fall rate evacuates clean water at a maximum rate of 93 GPM. If that device is flowing at 375 GPM and your clearing 93, then you are flooding at a rate of 282 GPM. 1. Professional liability: indoor flooding 3. The Real Flood Risks of indoor RPZs
  21. 21.  Inside a building 3 options for backflow preventer placement An article published June 2013 in the Chicago chapter of the American Society of Plumbing Engineers written by David DeBord, a former president of that organization, and current Education chair of the national ASPE, states all these facts better than I can. He uses the Manufacturer’s data supplied by a different manufacturer, and he uses a 65 PSI instead of my 85, but he actually does the math in the article and offers FLOOD rates or 219 GPM for 2 1/2 and 3”; and flood rate of 482 GPM for 4” and above. 1. Professional liability: indoor flooding 3 .The Real Flood Risks of indoor RPZs
  22. 22.  Inside a building 3 options for backflow preventer placement He concludes that regarding indoor RPZs… 1. Professional liability: indoor flooding 3. The Real Flood Risks of indoor RPZs
  23. 23.  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility The space provided for an indoor BPA is routinely inadequate as provided by the architect. That’s because giving up space that would otherwise add value is being allocated as non-revenue space. Non-revenue space is the enemy of every development project. The BPA pictured cost tens of thousands in property value. Even a mere 3” indoor BPA will cost a developer $6,000 to $9,000 more than an outdoor installation in a heated enclosure. 4. The Real Cost of Indoor BPAs
  24. 24. Charlotte: 32.000 SF Columbus: 36.000 SF Suffolk Cty: 33.333 SF Arlington: 32.000 SF Average: 33.325 SF Consider the average square footage required for just a 3-inch indoor in-line backflow preventer. To the right, four representative cities are represented. The average required space is 33.325 SF. Assuming a discount rate of 9%, rent value of $30 per foot annually, and a 25 year life, the net present value of that space to the property owner is $12, 156.48. Arlington, TX: 32 SF 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  25. 25. Average: 33.325 SF Annual Rent Value (based on Class A Office @ $30/sf) $999.75 25-year Cash Flows (based on 2.5% inflation) $34,149.22 Net Present Value (based on 9% discount rate) $12,156.48 Assuming a discount rate of 9%, rent value of $30 per foot annually, and a 25 year life, the net present value of that space to the property owner is $12, 156.48. 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  26. 26. NPV: Landlord has lost this amount of value by placing CBPA inside. $12,156.48 CONSIDER: 1.If space is recaptured for rental value, what will my alternative cost be? 2.Will placing the system outside cost more or less than $12,156.48? 3.If it’s less, then how much less? (I don’t like the look of a box outside.) 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  27. 27. Aboveground heated enclosure for 3” BPA with heat. Option A: Use conventional model e.i., Watts 957 NRS Safe-T-Cover 300-AL-H $3,266.00 72 X 38 X 22 = 60K CI Option B: Use new ”n-type” model e.i., Watts 957N NRS Safe-T-Cover 200SN-AL-H $1,120.00 46 X 38 X 19 = 33K CI 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  28. 28. $1,000 $1,120 $1,800 $3,920 $3,266 $1,200 $1,800 $6,266 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  29. 29. Indoor CBPA $3,920.00 plus assembly $6,266.00 plus assembly $12,156.48 plus assembly Owner’s Cost: 3” Domestic line 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  30. 30. “How much more value does my building have with the additional rent?” ANSWER: Year Annual Rent* 1 $999.75 PropertyValue* $10,289.09 5 $1,103.54 $11,357.23 10 $1,248.55 $12,849.67 15 $1,412.62 $14,538.22 20 $1,598.25 $16,448.66 25 $1,808.27 $18,610.15 * - Today’s dollars: Assumptions: Annual rent growth of 2.5%; 5% vacancy; 35% operating expenses; capitalization rate of 6%. Owner’s Property Value 4. The Real Cost of Indoor BPAs  Inside a building 3 options for backflow preventer placement 2. Space allocation/Accessibility
  31. 31. No more DCs on commercial or industrial properties. Chicagoland, IL TheexplosivegrowthoftheRPZ Elgin, October 2012 5. The Explosive Growth of the RPZ Naperville, April 2013 Naperville already required RPZs on their commercial irrigation systems, but after Elgin’s action, they too outlawed DCs, and in fact, extended mandatory RPZ use on fire line systems as well.
  32. 32. TheexplosivegrowthoftheRPZ Atlanta Area, GA Roswell, August, 2014 Roswell detailed two methods of RPZ placement, one indoors for small sizes, and one outdoors for larger sizes. The drawings for the indoor method explicitly address drain system requirements and force designers to reconcile the flood rate risks with specific drainage system capacities 5. The Explosive Growth of the RPZ
  33. 33. TheexplosivegrowthoftheRPZ Atlanta Area, GA Roswell, August, 2014 The chart shows that unless the designer is willing to install an 8” drain system all the way to the sewer inlet, he cannot utilize an indoor solution for any pipe size larger than 2 inches. 5. The Explosive Growth of the RPZ And the outdoor method mandates an enclosure that is ASSE-1060 compliant.
  34. 34. TheexplosivegrowthoftheRPZ Delaware, June 2013 Columbus Area, OH 5. The Explosive Growth of the RPZ
  35. 35. North central Texas Alpine Bedford Boerne Carrollton Cleburne College Station Denison Farmington Farris Franklin Grand Prairie Haltom Texarkana Waco Waskom White Settlement Addison Arlington Buda Cedar Hill Colleyville Crowley Denton Duncanville Fort Worth Franklin Gainesville Highland Village Midlothian Roanoke Round Rock Saginaw Same language added to muni code TheexplosivegrowthoftheRPZ 5. The Explosive Growth of the RPZ Fort Worth added this in 2010, since then many cities have added it as well.
  36. 36. TheexplosivegrowthoftheRPZ Central VA Lynchburg, 2008 Lynchburg has required RPZs on all non residential connections for almost a decade. This includes domestic, irrigation, and fire lines. 5. The Explosive Growth of the RPZ
  37. 37. TheexplosivegrowthoftheRPZ Mountain West Denver, February, 2013 In 2013 Denver Water added new standard details for 3” and larger RPZs to be installed outdoors. They also call for double checks for public park drinking fountains to be installed above ground in a heated enclosure. 5. The Explosive Growth of the RPZ
  38. 38. Seattle, WA Raleigh, NC Charlotte, VA Austin, TX Nashville, TN Albuquerque, NM Long Island, NY Denver, CO Las Vegas, NV Lynchburg, VA Columbus, OH Chicago. IL Forth Worth, TX Roswell, GA Longview, WA Arlington, TX Gwinnett Cty, GA Chesapeake, VA Olympia, WA Kent, WA Franklin, TN All these cities have made changes whereby RPZ use has been expanded either by lowering or eliminating the hazard threshold for use on domestic water lines in the past 5 years. (These are the cities we know of….) TheexplosivegrowthoftheRPZ 5. The Explosive Growth of the RPZ
  39. 39. Consider the ‘worst case scenario’ of a water volume discharge of a containment backflow prevention, namely, an uncontrolled discharge caused by a failure of the #1 check valve contemporaneous with the relief valve being stuck or propped open by debris. If there is no faucet demand within the commercial premise, such as over night, then this perfect storm produces an unmitigated flow of all available water through the relief valve continuously. The management of this sudden water deluge is a significant hazard. As severe as the most severe storm water runoff event. Special Insert This hazard is clearly work found within the civil engineering discipline rather than the plumbing engineering discipline. Designing and specifying any outdoor containment BPA – even if it is placed within the jurisdictional boundaries of the plumbing engineer, is asking for trouble. Watch a video of an RPZ doing what it’s designed to do here.
  40. 40. A survey of 1869 civil and mechanical engineers was conducted by Safe-T- Cover and EnviroDesign Management over a 22-month period ending in Spring, 2016. The survey followed a professional learning module delivered by EnviroDesign and was managed and tabulated by Benchmark Email Services. Excluding delivery failures, 1220 were delivered and opened. The following 2 slides show the questions in the short survey and the responses. 6. How do we Encourage transition to Civil Engineers
  41. 41. 6. How do we Encourage transition to Civil Engineers 1. Define your discipline. 2. The presentation added to my knowledge
  42. 42. 6. How do we Encourage transition to Civil Engineers 3. The information causes me to rethink my perspective on containment backflow preventer placement 4. The local water guidelines for commercial and industrial construction lack needed standard details for above-ground backflow preventer installation.
  43. 43.  Develop a firm-level policy  ASPE local chapter dialog with local water purveyor  Encourage best practices learning  Publish standard details and drawings consistent with best practices 6. How do we Encourage transition to Civil Engineers
  44. 44.  Plumbing engineers are facing new liability risks from insurance carriers, revealed by new warnings and commentary from industry leadership regarding indoor containment RPZs.  Because of the need for pure water in the public water supply and the undetectable nature of the DCs, purveyors are demanding more RPZs and ignoring the legacy hazard guidance.  RPZs are designed to engulf the immediate surrounding area.  Indoor placement of 3” & larger RPZs adds irrational risk for PO & designer.  Placing the CBPA inside costs PO $000s more than outside.  The need to address sudden flood water flows disqualifies MEP from CBPA Design.  Your local water district must be encouraged to adopt new details and guidelines that promote best practices and adoption by CEs. Take-Aways

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