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Backflow Prevention

Backflow Prevention. "Backflow Prevention... Practiced by a few, Understood by some, Misunderstood by many, Ignored by thousands...". NZWWA. What Causes Backflow. Backflow is the potential cross contamination of a contaminant into a potable water supply.

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Backflow Prevention

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  1. Backflow Prevention

  2. "Backflow Prevention...Practiced by a few,Understood by some,Misunderstood by many,Ignored by thousands..." NZWWA

  3. What Causes Backflow • Backflow is the potential cross contamination of a contaminant into a potable water supply. • There are two conditions that can cause a backflow. • Back-syphonage • Back-pressure

  4. Back- Syphonage What is back-syphonage?Back-siphonage is the reversal of normal flow in a system caused by a negative pressure (vacuum or partial vacuum) in the supply piping. What factors can cause back-syphonage? Back-syphonagecan be created when there is a stoppage of the water supply due to nearby fire fighting, repairs or breaks in city main, etc. The effect is similar to the sipping of an ice cream soda by inhaling through a straw, which induces a flow in the opposite direction.

  5. “Back Syphonage” Recommended installation of hose bib vacuum breaker

  6. Back-Pressure What is backpressure backflow? Backpressure backflow is the reversal of normal flow in a system due to an increase in the downstream pressure above that of the supply pressure. What factors can cause a back-pressure backflow condition? Backpressure-backflow is created whenever the downstream pressure exceeds the supply pressure, which is possible in installations such as heating systems, elevated tanks, and pressure-producing systems. As water tends to flow in the direction of least resistance, a backpressure-backflow condition would be created and the potentially contaminated water would flow into the potable water supply.

  7. Back-Pressure

  8. Backflow History New Zealand • Metro Water (Auckland City Council) were one of the first councils in New Zealand to put an active Backflow program in place. • Headed up by Bill Clarke: Three inspectors reviewed all commercial properties within their region. • The inspectors checked for potential cross connections. If a cross connection was identified, boundary protection needed to be installed. • Internal protection is covered under G12

  9. Backflow History New Zealand • The focus was initially on high risk properties including • Hospitals, Mortuaries, Dentists and Heavy industrial plants • A five year plan was put in place to check all commercial properties. • If my memory serves me correctly, 40% of properties inspected had cross connections identified and needed backflow devices installed. • Today all councils have developed a Backflow program and in many cases Backflow is required all new commercial and domestic connections.

  10. CROSS CONNECTIONS CAN HAPPEN ANYWHERE, ANYTIME WITHOUT WARNING!

  11. Examples of Backflow ContaminationCases in New ZealandThe following are actual documented cases.

  12. Cross Connection Examples • Farming family: stomach cramps, diarrhoea, vomiting and oral anaesthesia. • Cause: inline stock dispenser adding supplement to cattle trough through water feed line. • Hotel: foaming soap-like bubbles coming from the cold water supply at the kitchen ... shocking tasting water. • Cause: soap dispenser was connected to the domestic supply line. • New Zealand Fire Service: complaint that the water supply changed colour while dousing out a plastic fire. • Cause: the fire truck started up its booster pump thus drawing excess water from our main and causing a reverse action to the supply line, drawing paint from a vat in a paint factory two premises down the road.

  13. Cross Connection Examples • Private Residence: grass clippings in toilet bowl and kitchen sink. • Cause: Compost bin in yard had a garden hose left running in it and when the mains supply was cut, a negative pressure resulted in backflow to the dwelling. • Factory: green slime and globbythings came out of the tap. • Cause: Head tank did not have an adequate air separation and the valve was under water. • Factory: Complaint of air entering the water supply and poor water pressure. • Cause: A cross connection to the cooling jacket on an air compressor in a nearby panel beating repair shop resulted in a direct connection to the inner jacket and holding tank, thus letting air into the system.

  14. Cross Connection Examples • Race Course: Funny tasting water and soft drinks at the post mix machine ... metallic tasting. • Cause: The post mix dispenser was connected to C02 gas from a cylinder. Debris had passed through the strainer which was not a ball check valve. • Burst Water Mains: Contractors on site found patches of foam and warm water running through the open water main. • Cause: Backflow from hot water cylinders and commercial dish washing machines in restaurants and high rise buildings. • Factory: 120 staff were sent home with stomach cramps, gastric complaints, and headaches ... foul tasting water. • Cause: The factory processes newspaper into pulp, the tank are filled with a mixture of alum and water from the domestic supply. A cross connection occurred when an underwater inlet was installed during maintenance work on the internal plumbing.

  15. Cross Connection Examples • Commercial Property: Bad tasting and smelly water. • Cause: Tenant on the premise had a leaking tap, and couldn't contact the owner so a garden hose was attached to the hose cock and stuffed down the sewer line. When the water main pressure was reduced, back syphonageoccurred, causing sewer gases to enter the premise and water supply through the hose cock. • Restaurant: Blue water at the sink and a funny smell. • Cause: Toilet duck blocks had been put into the head tank feeding the WC facilities. The valve were under water, a cross connection existed and resulted in the kitchen domestic supply being polluted. • Commercial Property (Multi-Storey Building): Strange taste, smell and black colour to the drinking water. • Cause: One of the dual head pumps failed, the other one was disconnected, removed and breaching pipe work was installed. This was re-plumbed into the fire service by mistake resulting in back pressure whereby the contaminated fire water lowed into the drinking supply and surrounding area.

  16. Cross Connection Examples • Restaurant: Strange unidentified crystallised particles coming out of the cold faucet in the kitchen, had a strange smell and looked like tiny brown glass beads. • Cause: A large coffee machine was connected to the boiler, creating pressurised boiling water which back flowed into the filter system, causing it to disintegrate. This formed a residue of calcium sulphate in resin beads, contaminating the drinking water. • Industrial Site: Tenants complained of poor water quality, a strange taste and smell. • Cause: Another tenant in the building had set up a commercial soft drink manufacturing plant. A cross connection with the base material and drinking water resulted in the adjoining tenants supply being contaminated. • High Rise Units: Experienced hot water at their water meter. • Cause: A negative pressure was caused during maintenance work on the public main, and hot water had back-siphoned from mains-pressure hot water cylinders. There was danger of these tanks imploding.

  17. Cross Connection Examples • Wholesale Meat Processing Factory: Employees complained of a funny taste in the lunch room water supply. • Cause: The meat extrusion machine used a hydraulic ram and bladder system to produce sausages. A cross-connection was found with the fire service line. When the preparation area was washed down using it, the pressure in the domestic line dropped resulting in back siphon age. Blood and other contaminants entered the water due to this. • Private Residence In A Basement Flat: Strange taste in the drinking water. • Cause: An improvised bidet in an upstairs flat had been constructed using a small garden hose which was left lying in the toilet bowl when not in use. The owner of the building turned off the water supply creating negative pressure resulting in back siphon age and a cross connection with the sewer.

  18. Cross Connection Examples • Automotive Engine Reconditioning Company (large trucks): Workshop water was reported as having a diesel taste and smell coming from the taps in the staff lunch room. • Cause: A cross connection to the oil bath was discovered in the diesel yard which resulted in a small amount of diesel sucked into the water line when maintenance work was being carried out on the main in the street. • Private Residence: Complained of excessive water hammer and rusty discolouration of their drinking water. • Cause: A backflow was discovered from the hydraulic lift used to lift a wheel chair to a higher level.

  19. Cross Connection Examples • Motor Rebuilding Premises: Strange taste to the water which made it undrinkable. • Cause: A backflow was discovered from the workshop toilet to the staff cafeteria kitchen sink. • Multi-story Building: Oily taste in the drinking water. • Cause: Back syphonageoccurred at the same time painters were working on the roof. The head tank had a coating of paint on the surface, paint was sucked into the supply line and up to the roof tank when the distribution main dropped in pressure. You may have heard about the recent major water contamination situation in Havelock north NZ that struck down 3500 people with illness and resulted in 3 deaths. This is still under investigation but was caused by contaminated water.

  20. Hazard Definitions • Low Hazard: If a Backflow situation should arise and enter into the potable water supply this would constitute a nuisance i.e.: not cause illness like hot entering the cold water line. • These are a non testable device • If in doubt install a Testable High or Medium hazard device. • Normally domestic connections have a non testable dual check valve or a manifold containing a dual check valve.

  21. Hazard Definitions • Medium Hazard: If a Backflow should arise and enter into the potable water supply this would constitute a nuisance i.e.: causes a bad taste / odour or minor illness. • If in doubt install a high hazard device

  22. Double Check Valve (DCV) • ApplicationThis is a testable device designed for use in Medium Hazard conditions to prevent backflow caused by back syphonageor back pressure. It is intended for use under continuous pressure conditions. • Components Non return valves - Two independently acting non-return valves shall be provided and arranged to be force-loaded to the closed position.

  23. Double Check Valve (DCV) • Specific design requirements • Test taps shall be provided in the device upstream of the upstream non-return valve, downstream of the downstream non-return valve, and in the intermediate chamber. • Performance tests • Non-return valve closing pressure each non-return valve shall not leak against pressures up to 7 kPa applied in the direction of normal water flow, with the pressure downstream at atmospheric pressure.

  24. Double Check Valve (DCV)

  25. Hazard Definitions • High Hazard:If a Backflow should arise and enter into the potable water supply causing death, illness, spread disease, or a high probability of causing such effects. • Hospitals, mortuaries, dentists, hair dressers etc. • You would be amazed at what some people do on industrial sites with your water supply.

  26. Reduced Pressure Zone Assembly (RPZ) • APPLICATION • This is a testable device designed for use in High Hazard conditions to prevent backflow caused by back syphonageor back pressure. It is intended for use under continuous pressure conditions. • COMPONENTS • Non-return valves Two independently acting non-return valves in series which are arranged to be force-loaded to the closed position. • Relief valve A relief valve, positioned between the non-return valves, arranged to be forced-loaded to open to atmosphere, whenever the pressure differential across the upstream non-return valve reduces to 14 kPa. • Test taps Test taps shall be provided to enable regular checking of the performance of the non-return valves and the relief valve.

  27. Reduced Pressure Zone Assembly (RPZ) • All RPZ devices require an adequate drain, At least twice the size of the Device • Must be constructed to AS/NZS 2845.3 • Suitable for continuous and non continuous pressure installations • Must be installed in an accessable place for servicing and testing • Must be protected from extreme temperature and toxic environments

  28. Reduced Pressure Zone Assembly (RPZ) • Specific Design Requirements • Relief valve diaphragm or equivalent shall be installed in a manner which, in case of failure, shall produce visible evidence of failure.

  29. Reduced Pressure Zone Assembly (RPZ)

  30. New Zealand Installation Requirements

  31. Installation Requirements • Only qualified plumbers can install and maintain backflow devices inside the boundary. • Backflow devices should be installed near as practicable to the potential source of contamination. • All backflow devices must be installed with two resilient seated Isolation valves and Y-Strainer except on firelines • All pipe lines should be thoroughly flushed to remove foreign materials. • Install with arrow facing in direction of flow. • In an Accessible position for maintenance & testing as per AS/NZS 2845 • Protected from heat, freezing, corrosion, physical damage & toxic environments (G12).

  32. Installation Requirements • Can only be bypassed with a valve of the same hazard rating. (G12) • Backflow devices must be tested by an ABT/ IQP including newly installed valves. • Two smaller devices can be piped in parallel to serve a larger supply where interruptions for testing & servicing would be unacceptable i.e. hospital • Installations subject to water hammer should be protected with the use of non-return valves and arrestors. • Tested every 12 months to obtain Building Warrant of Fitness.

  33. IMPORTANT ALL BACKFLOW DEVICES REDUCE VOLUME AND PRESSURE

  34. Example of 20mm DCV Flow Charts. Manufacturers Maximum flow rate is the maximum velocity that water should be passing through device. Any more and it can cause damage to device. The faster water travels the greater the pressure loss due to friction.

  35. RPZFlow Rates

  36. Plumbing Backflow Kitset

  37. Backflow Cabinets

  38. Backflow Regulations • 1961 -Water Supply Regulations required Boundary Backflow Protection to protect potable supply. Administered by Health Department. • Most councils are only interested in protecting there water supply network. ie: boundary protection • 1992 -Building Industry Authority (BIA) in G12 acceptable solutions require Backflow Protection at point of possible contamination. (To protect people inside the building). Administered by Internal Affairs. • Internal Zone protection inside the building.

  39. Backflow Regulations • 2003 -A change to the Drinking water Legislation did away with 61 Regulations and called up the Public Health Risk Management Plan(PHRMP), which required Backflow Protection at every connection. The water supply managed group of the NZWWA funded a Backflow code of practice as a method of compliance to the PHRMP. The Backflow code of practice is for Boundary Protection only and was written by the Backflow Special Interest Group of the NZWWA for the water supply managers. This code was formally adopted by all public and private water suppliers in New Zealand.

  40. Boundary Backflow Prevention for Drinking Water Supplies 2013 (Backflow code of practice)

  41. Summary of the Code • Only plumbers can work on devices inside the boundary. • Testers will be called. Approved Backflow Technicians (ABT) and pass an approved 40hr course. • Testers registered, as ABT must be individuals not companies. • Test kits must be recalibrated. The lesser of 12 months or 200 tests. • Endorsed licences to test devices on fire lines by passing additional approved courses.

  42. Summary of the Code • Backflow surveyors must complete an approved course of 24hrs extra above ABT requirement. • Register of ABT tests and surveyors to be held by NZWWA. • ABT must be recertified every 3 years. • Surveying is the most important part of any backflow program.

  43. G12 Building Code

  44. G12 Building Code

  45. G12 Building Code

  46. Backflow training is now part of a Plumbing Apprentices training curriculum

  47. Q & A

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