Advanced Backflow Prevention Internet Course 1 Hour

Transcription

1 Advanced Backflow Prevention Internet Course 1 Hour

2 The Potable Water Supply Can you imagine a world without it? Unhealthy Inconvenient In a word, chaos Society as we know it would be unsustainable. I would argue that the supply of potable water is the most important innovation known to man.

3 With that thought in mind, this one hour course will discuss section 608 of the 2007 Florida Building Code, plumbing.

4 Protecting the potable water supply, section 608 of the Florida Building Code, plumbing

5 The Florida Building Code, Plumbing 2007 definition of POTABLE WATER. Water free from impurities present in amounts sufficient to cause disease or harmful physiological effects and conforming to the bacteriological and chemical quality requirements of the Public Health Service Drinking Water Standards or the regulations of the public health authority having jurisdiction.

6 Section 608 Protection of Potable Water Supply General. A potable water supply system shall be designed, installed and maintained in such a manner so as to prevent contamination from nonpotable liquids, solids or gases being introduced into the potable water supply through cross-connections or any other piping connections to the system. Backflow preventer applications shall conform to Table 608.1, except as specifically stated in Sections through

7 The Florida Building Code, Plumbing 2007 definition of a WATER SUPPLY SYSTEM. The water service pipe, water distribution pipes, and the necessary connecting pipes, fittings, control valves and all appurtenances in or adjacent to the structure or premises.

8 The Florida Building Code, Plumbing 2007 definition of PUBLIC WATER MAIN. A water supply pipe for public utilization controlled by public authority.

9 The Florida Building Code, Plumbing 2007 definition of WATER PIPE Riser. A water supply pipe that extends one full story or more to convey water to branches or to a group of fixtures. Water distribution pipe. A pipe within the structure or on the premises that conveys water from the water service pipe, or from the meter when the meter is at the structure, to the points of utilization. Water service pipe. The pipe from the water main or other source of potable water supply, or from the meter when the meter is at the public right of way, to the water distribution system of the building served.

10 The Florida Building Code, Plumbing 2007 definition of PLUMBING FIXTURE. A receptacle or device that is either permanently or temporarily connected to the water distribution system of the premises and demands a supply of water there from; discharges wastewater, liquid-borne waste materials or sewage either directly or indirectly to the drainage system of the premises; or requires both a water supply connection and a discharge to the drainage system of the premises

11 The Florida Building Code, Plumbing 2007 definition of PLUMBING APPURTENANCE. A manufactured device, prefabricated assembly or an on-the-job assembly of component parts that is an adjunct to the basic piping system and plumbing fixtures. An appurtenance demands no additional water supply and does not add any discharge load to a fixture or to the drainage system.

12 The Florida Building Code, Plumbing 2007 definition of CONTAMINATION. An impairment of the quality of the potable water that creates an actual hazard to the public health through poisoning or through the spread of disease by sewage, industrial fluids or waste.

13 The Florida Building Code, Plumbing 2007 does not require some water supplies to be protected by backflow prevention programs. An example would be individual water supply wells.

14 The Florida Building Code, Plumbing 2007 definitions of INDIVIDUAL WATER SUPPLY. A water supply that serves one or more families, and that is not an approved public water supply. WELL Bored. A well constructed by boring a hole in the ground with an auger and installing a casing. Drilled. A well constructed by making a hole in the ground with a drilling machine of any type and installing casing and screen. Driven. A well constructed by driving a pipe in the ground. The drive pipe is usually fitted with a well point and screen. Dug. A well constructed by excavating a large-diameter shaft and installing a casing.

15 What is a cross-connection?

16 608.6 Cross-connection control. Cross connections shall be prohibited, except where approved protective devices are installed.

17 The Florida Building Code, Plumbing 2007 definition of a Cross Connection Any physical connection or arrangement between two otherwise separate piping systems, one of which contains potable water and the other either water of unknown or questionable safety or steam, gas or chemical, whereby there exists the possibility for flow from one system to the other, with the direction of flow depending on the pressure differential between the two systems (see Backflow ).

18 Or more simply put, a cross-connection is when potable water is connected to nonpotable water. The Florida Building Code, Plumbing 2007 definition of NON POTABLE WATER. Water not safe for drinking, personal or culinary utilization.

19 Cross-connections are the physical connections that allow backflows. If crossconnections are not present, then the backflow of contaminants into the potable water supply cannot happen. So, it is important to know how and why crossconnections are created.

20 Types of cross-connections There are two types of cross-connections Temporary Permanent1

21 Temporary cross-connections are when the potable water supply is temporarily connected to a non-potable source. Hoses connected to the permanent water supply line are an example.

22 The most common cause of crossconnections is believed to be a garden hose. A hose used to fill a pool. A hose sitting in a puddle of water A hose connected to a faucet A hose used to fill or clean a tank truck A hose used to clean a drainage system

23 The Florida Building Code, Plumbing 2007 definition of FAUCET. A valve end of a water pipe through which water is drawn from or held within the pipe.

24 The Florida Building Code, Plumbing 2007 definition of DRAINAGE SYSTEM. Piping within a public or private premise that conveys sewage, rainwater or other liquid wastes to a point of disposal. A drainage system does not include the mains of a public sewer system or a private or public sewage treatment or disposal plant.

25 The Florida Building Code, Plumbing 2007 definition of SWIMMING POOL. Any structure, basin, chamber or tank containing an artificial body of water for swimming, diving or recreational bathing having a depth of 2 feet (610 mm) or more at any point.

26 Hose connections. Sillcocks, hose bibbs, wall hydrants and other openings with a hose connection shall be protected by an atmospheric-type or pressure- type vacuum breaker or a permanently attached hose connection vacuum breaker.

27 Temporary cross-connections are created when tank trucks connect to the potable water supply to fill their trucks. Lawn maintenance, pesticide, fire, jet trucks and sludge trucks can all create temporary cross-connections.

28 Fire fighters can pump water from ponds or other non-potable sources through their tank trucks. If the tanks are not thoroughly disinfected before being connected to potable water lines, it is possible for contamination of the potable water supply through backflow to occur.

29 One of the most hazardous temporary cross-connections are caused by siphon mixers. Siphon mixers are attached to hoses for fertilization or pest control. If there were a loss in water pressure a backflow could occur, causing the chemical to be drawn into the water supply.2

30 Permanent cross-connections are when the water supply line is connected to a non-potable source using a fixed extension of the water supply.

31 Some examples can be: Air cooling systems Boilers Holding vessels Lab equipment Food processing equipment Fixed unintentional connection to a non-potable water source (ex. potable water supply lines connected to waste water pipes or an irrigation system using reclaimed water.)

32 The Florida Building Code, Plumbing 2007 definition of FIXTURE FITTING Supply fitting. A fitting that controls the volume and/or directional flow of water and is either attached to or accessible from a fixture, or is used with an open or atmospheric discharge. Waste fitting. A combination of components that conveys the sanitary waste from the outlet of a fixture to the connection to the sanitary drainage system.

33 The Florida Building Code, Plumbing 2007 definition of RECLAIMED WATER. Water that has received treatment and is reused after flowing out of a domestic wastewater treatment facility.

34 608.2 Plumbing fixtures. The supply lines and fittings for every plumbing fixture shall be installed so as to prevent backflow. Plumbing fixture fittings shall provide backflow protection in accordance with ASME A

35 The Florida Building Code, Plumbing 2007 definition of FIXTURE SUPPLY. The water supply pipe connecting a fixture to a branch water supply pipe or directly to a main water supply pipe.

36 The Florida Building Code, Plumbing 2007 definition of PLUMBING APPLIANCE. Any one of a special class of plumbing fixtures intended to perform a special function. Included are fixtures having the operation or control dependent on one or more energized components, such as motors, controls, heating elements, or pressure- or temperature-sensing elements. Such fixtures are manually adjusted or controlled by the owner or operator, or are operated automatically through one or more of the following actions: a time cycle, a temperature range, a pressure range, a measured volume or weight

37 Cross-connections are usually created by a lack of knowledge or if a person is knowledgeable, negligence.

38 What is a backflow?

39 The Florida Building Code, Plumbing 2007 definitions of a BACKFLOW. Pressure created by any means in the water distribution system, which by being in excess of the pressure in the water supply mains causes a potential backflow condition. BACKFLOW CONNECTION. Any arrangement whereby backflow is possible

40 A backflow is a flow of water through a cross-connection in the opposite direction in which it was intended to flow. This flow is caused by a pressure differential. Water flows in response to differentials in air or water pressure. Flow is from greater pressure to lesser.3

41 Pressure differentials in water can be caused by the column height, volume, atmospheric pressure, temperature, velocity, and mechanical devices like pumps.4

42 Pressure differentials can cause a reversal of normal flow direction and a backflow of hazardous fluids if a cross-connection is present.

43 There are two types of backflow. Back pressure Backsiphonage5

44 The Florida Building Code, Plumbing 2007 definition of Backpressure, low head. A pressure less than or equal to 4.33 psi (29.88 kpa) or the pressure exerted by a 10-foot (3048 mm) column of water

45 Back pressure is the most common backflow. It happens when the pressure exerted by the non-potable hazard is greater than the pressure from the potable supply system.6

46 The Florida Building Code, Plumbing 2007 definition FLOW PRESSURE. The pressure in the water supply pipe near the faucet or water outlet while the faucet or water outlet is wide open and flowing.

47 Back pressure can occur when the water pressure from the potable supply is decreased, the non-potable pressure is increased or both conditions exist.

48 Potable water supply pressure is decreased when there is a water main break, fire fighting, line flushing, and water line leaks.

49 Back pressure can occur from the following: Boilers Air to water heat exchangers Irrigation wells Chemical storage tanks Water heaters with malfunctioning T&P valves

50 The Florida Building Code, Plumbing 2007 definitions of Temperature and pressure relief (T&P) valve. A combination relief valve designed to function as both a temperature relief and a pressure relief valve. WATER HEATER. Any heating appliance or equipment that heats potable water and supplies such water to the potable hot water distribution system.

51 Boilers build up back pressure due to high temperatures. They can be especially hazardous because boilers are often cleaned with boric nitrate which is toxic. Boric nitrate is used to prevent scale from forming inside the boiler.

52 Connections to boilers. The potable supply to the boiler shall be equipped with a backflow preventer with an intermediate atmospheric vent complying with ASSE 1012 or CSA B64.3. Where conditioning chemicals are introduced into the system, the potable water connection shall be protected by an air gap or a reduced pressure principle backflow preventer, complying with ASSE 1013, CSA B64.4 or AWWA C511.

53 Chemical storage tanks are often crossconnected with potable water to dilute the chemicals held in storage. Often pumps are used to maintain pressure within the tanks for the dispensing of the chemicals held. If the pressure in the tanks exceeds the pressure of the potable water supply, back pressure will occur.

54 Backsiphonage is the second type of backflow. It occurs when the potable water supply pressure falls to negative pressure. Negative pressure is pressure less than atmospheric pressure of 14.7 p.s.i..7

55 The Florida Building Code, Plumbing 2007 definition of Backsiphonage. The backflow of potentially contaminated water into the potable water system as a result of the pressure in the potable water system falling below atmospheric pressure of the plumbing fixtures, pools, tanks or vats connected to the potable water distribution piping.

56 Some of the common causes of backsiphonage are: Fire fighting Water main breaks Line flushing

57 The Florida Building Code, Plumbing 2007 definition of WATER MAIN. A water supply pipe or system of pipes, installed and maintained by a city, township, county, public utility company or other public entity, on public property, in the street or in an approved dedicated easement of public or community use.

58 Flow direction is reversed when the water supply pressure is reduced below 14.7 psi, simply because, atmospheric pressure of 14.7 psi, is exerted on the non-potable sources. So, if a cross-connection exists the non-potable source will contaminate the water supply.

59 In order to protect the potable water supply it is important to know the causes of backflow. It is also important to be aware of the physical connections (crossconnections), which give backflows a connection to potable water supplies. Potable water systems must be examined for cross-connections and conditions which might create pressure differentials.

60 Now that you understand what crossconnections and backflows are, let s talk about backflow prevention.

61 608.3 Devices, appurtenances, appliances and apparatus. All devices, appurtenances, appliances and apparatus intended to serve some special function, such as sterilization, distillation, processing, cooling, or storage of ice or foods, and that connect to the water supply system, shall be provided with protection against backflow and contamination of the water supply system. Water pumps, filters, softeners, tanks, commercial drinking water dispensers and all other appliances and devices that handle or treat potable water shall be protected against contamination.

62 Backflow protection. Means of protection against backflow shall be provided in accordance with Sections through

63 Backflow prevention is paramount in protecting the potable water supply. Backflow prevention can be classified as either a method or a mechanism.8

64 The Florida Building Code, Plumbing 2007 definition of a BACKFLOW PREVENTER. A device or means to prevent backflow.

65 A method of preventing backflows is simply preventing cross-connections by the use of air gaps and differentiating between potable water lines and nonpotable lines.

66 Air gaps prevent backflow by eliminating the physical condition which allows backflow to occur (cross-connections). Air gaps are simply the space between the outlet of a potable supply and the flood rim level of a receptacle.

67 The Florida Building Code, Plumbing 2007 definition of FLOOD LEVEL RIM. The edge of the receptacle from which water overflows.

68 Air gap. The minimum required air gap shall be measured vertically from the lowest end of a potable water outlet to the flood level rim of the fixture or receptacle into which such potable water outlet discharges. Air gaps shall comply with ASMEA and air gap fittings shall comply with ASME A

69 The Florida Building Code, Plumbing 2007 definition of WATER OUTLET.A discharge opening through which water is supplied to a fixture, into the atmosphere (except into an open tank that is part of the water supply system), to a boiler or heating system, or to any devices or equipment requiring water to operate but which are not part of the plumbing system

70 The Florida Building Code, Plumbing 2007 definition of an AIR GAP (Water Distribution System). The unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet supplying water to a tank, plumbing fixture or other device and the flood level rim of the receptacle.

71 Air gaps are considered the best protection against backflow because they require no parts and if installed correctly are fail proof. Some of the draw backs with air gaps is that they are easily circumvented and water pressure must be recreated if distribution is required downstream of the air gap.9

72 If an air gap is insufficient, the friction in water can allow water to reverse direction given enough vacuum. Therefore it is important to maintain the minimum air gaps.

73 Color coding pipes to distinguish potable water from non-potable sources is another important step in preventing crossconnections. This should not be overlooked with the increasing trend of reclaimed water programs in use.

74 608.8 Identification of potable and non potable water. In all buildings where two or more water distribution systems, one potable water and the other nonpotable water, are installed, each system shall be identified either by color marking or metal tags as required by ASME A13.1. Reclaimed water systems shall be identified using color-coded Pantone Purple 522C and marked with the statement NONPOTABLEWATER NOT FOR HUMAN CONSUMPTION.

75 If cross-connections cannot be avoided, a physical barrier or mechanism must be installed to isolate backflows. This mechanism is called a backflow preventer.

76 The installation of a mechanical backflow preventer above the critical level.

77 The Florida Building Code, Plumbing 2007 definition of CRITICAL LEVEL (C-L). An elevation (height) reference point that determines the minimum height at which a backflow preventer or vacuum breaker is installed above the flood level rim of the fixture or receptor served by the device. The critical level is the elevation level below which there is a potential for backflow to occur. If the critical level marking is not indicated on the device, the bottom of the device shall constitute the critical level.

78 Backflow preventers are classified as different types: Atmospheric Vacuum Breaker (AVB) Pressure Vacuum Breaker (PVB) Double Check Valve Assembly (DCVA) Reduced Pressure Principle Assembly (RP)

79 Atmospheric Vacuum Breaker s are made up of a single check valve and an air inlet. When water pressure is above atmospheric pressure of 14.7 psi the check valve is pushed up to close the air inlet. If the pressure drops below 14.7 psi the check valve closes and air is introduced to the water line, essentially creating an air gap.10

80 The Florida Building Code, Plumbing 2007 definition of VACUUM. Any pressure less than that exerted by the atmosphere. VACUUM BREAKER. A type of backflow preventer installed on openings subject to normal atmospheric pressure that prevents backflow by admitting atmospheric pressure through ports to the discharge side of the device

81 Atmospheric-type vacuum breakers. Pipeapplied atmospheric-type vacuum breakers shall conform to ASSE 1001 or CSA B Hose-connection vacuum breakers shall conform to ASSE 1011, ASSE 1019, ASSE 1035, ASSE 1052, CSA B64.2, CSA B64.2.1, CSA B , CSAB or CSAB64.7. These devices shall operate under normal atmospheric pressure when the critical level is installed at the required height.

82 The draw back of Atmospheric Vacuum Breaker s is they do not work in a back pressure situation since the check valve stays in the up position. They only work in backsiphonage situations and they are not testable.

83 Atmospheric Vacuum Breaker s cannot be used under conditions of continuous water pressure because the check valve gets stuck in the air inlet. The check valves on Atmospheric Vacuum Breaker s do not have springs to seat them when the water flow is stagnant.11

84 Pressure Vacuum Breaker s differ from Atmospheric Vacuum Breaker s in that the air inlet s and check valve s are isolated from each other with self contained springs. Pressure Vacuum Breaker s are also testable and contain two shut off valves which classifies Pressure Vacuum Breaker s as assemblies.

85 Pressure-type vacuum breakers. Pressure-type vacuum breakers shall conform to ASSE 1020 or CSA B and spillproof vacuum breakers shall comply with ASSE These devices are designed for installation under continuous pressure conditions when the critical level is installed at the required height. Pressure-type vacuum breakers shall not be installed in locations where spillage could cause damage to the structure.

86 Pressure Vacuum Breaker s can be used under continuous water pressure conditions. When the water flow is stagnant, the check valve is closed by it s spring. If the water pressure drops to 15.7 psi the air inlet opens creating an air gap. The air inlet is equipped with a spring that opens at 1 psi.12

87 Pressure Vacuum Breaker s are used mostly in irrigation systems, but since they should not be subjected to back pressure, they must be installed at least 12 above the highest outlet downstream. PVB s can be used in health and non health hazard situations.13

88 Double check-valve assemblies. Double check valve assemblies shall conform to ASSE 1015, CSAB64.5, CSA B or AWWA C510. Double-detector check-valve assemblies shall conform to ASSE These devices shall be capable of operating under continuous pressure conditions.

89 The Double Check Valve is an assembly since, it comes with two shut off valves and is testable. They consist of two check valves both of which have self contained springs. Double check valve s provide protection against back pressure and back siphonage.

90 With Double Check Valve s each check valve should hold tight against at least 1 psi in the direction of flow. The maximum allowable pressure loss across the whole device is 10 psi. This is necessary since these devices are most frequently used in fire sprinkler systems, where the amount of flow required needs to accounted for.14

91 Connections to automatic fire sprinkler systems and standpipe systems. The potable water supply to automatic fire sprinkler and standpipe systems shall be protected against backflow by a double check-valve assembly or a reduced pressure principle backflow preventer. Exceptions: 1. Where systems are installed as a portion of the water distribution system in accordance with the requirements of this code and are not provided with a fire department connection, isolation of the water supply system shall not be required. 2. Isolation of the water distribution system is not required for deluge, preaction or dry pipe systems.

92 This is a double check valve assembly on a fire sprinkler system, being flushed clean.

93 Reduced Pressure Principle Assembly or the RP is the final assembly. It is testable and contains two shut off valves making it an assembly. It consists of two check valves, the first of which must reduce pressure by at least 5 psi, the second check valve by at least 1 psi. Additionally, the Reduced Pressure Principle Assembly contains a relief valve.

94 Reduced pressure principle backflow preventers. Reduced pressure principle backflow preventers shall conform to ASSE 1013, AWWA C511, CSA B64.4 or CSA B Reduced pressure detector assembly backflow preventers shall conform to ASSE These devices shall be permitted to be installed where subject to continuous pressure conditions. The relief opening shall discharge by air gap and shall be prevented from being submerged.

95 The Florida Building Code, Plumbing 2007 definition of REDUCED PRESSURE PRINCIPLE BACKFLOW PREVENTER. A backflow prevention device consisting of two independently acting check valves, internally force-loaded to a normally closed position and separated by an intermediate chamber (or zone) in which there is an automatic relief means of venting to the atmosphere, internally loaded to a normally open position between two tightly closing shutoff valves and with a means for testing for tightness of the checks and opening of the relief means.

96 The Florida Building Code, Plumbing 2007 definition of a RELIEF VALVE Pressure relief valve. A pressureactuated valve held closed by a spring or other means and designed to relieve pressure automatically at the pressure at which such valve is set.

97 The relief valve is made up of a diaphragm and a spring. The spring has between a 2 to 3 psi tension. This spring applies pressure to open the relief valve.

98 The relief valve is located between the first and second check valves, this area is called the relief zone. The relief valve s diaphragm and spring are put under pressure by the water supply, before the first check valve. On the other side of the diaphragm pressure from the relief zone and the spring is applied. The water pressure from this zone is reduced by the first check valve, therefore more water pressure is applied from the supply side. This water supply pressure works to close the relief valve. The relief valve is designed to open to the atmosphere to provide an air gap if certain conditions are met.

99 The Reduced Pressure Principle Assembly offers the highest degree of protection of all the assemblies. RP s are used for health and non health hazards. It is the most versatile backflow preventer. The air gap still provides better protection against backflow but since it requires a complete loss of water pressure, it is not practical for all applications.15

100 Some of the conditions which will open the relief valve are: A lack of pressure from the utility An equal amount of water pressure on both sides of the diaphragm More pressure in the relief zone than supplied from the utility

101 Testing backflow assemblies is important because they do not always operate as intended. Water flowing through them can bring debris, deposits and eventually wear out the parts inside.

102 The following backflow assemblies can be tested: Pressure Vacuum Breaker Double Check Valve Assembly Reduced Pressure Principle Assembly

103 Testing is accomplished by the use of a test kit. There are three types of test kits: Sight tube Duplex gauge Differential gauge16

104 A sight tube is simply a plastic tube adapted to fit the test cocks on backflow prevention assemblies. It is used to test a double check valve assembly.

105 The sight tube is filled with 28 inches of water from the test cock directly downstream of the check valve to be tested. The 28 inch water column created by the sight tube, applies 1 psi of water pressure to the backside of the check valve. Once the shutoff valve s are closed, this water column determines if the check valve will hold 1 psi.

106 A Duplex Gauge is also used to test double check valve assemblies. The reason it is called a duplex gauge is that it has essentially two gauges combined on one face. The control valves on the duplex gauge are used to control the flow of water pressure and bleed air from the valve.

107 When using a duplex gauge to test a double check valve assembly, 2 psi of back pressure, is applied to the check valve being tested. If the check valve can hold this pressure, a confirmation test is done, were the back pressure is increased to 5 psi.17

108 A problem with using a sight tube or a duplex gauge for testing double check valve assemblies is that both shutoff valves must be closed for the test. Often with older shutoff valves debris is dislodged when this happens, fouling the check valves.

109 The preferred method of testing double check valves is with a differential gauge. The test with a differential gauge does not require the first shutoff valve to be closed, eliminating the potential fouling of a working backflow assembly.

110 Differential gauges get there name from the fact that they measure the difference in pressure on one side of the check valve compared to the other side of the check valve.

111 Differential gauges can be used to test pressure vacuum breakers, double check assemblies and reduced pressure principle assemblies.

112 All testable backflow preventer assemblies, pressure vacuum breakers, double check valve assemblies, and reduced pressure principle assemblies, should be tested once a year. Most water departments require testing be reported to them yearly on test forms filled out by the tester.18

113 Repair of Backflow Preventer Assemblies

114 Backflow preventer assemblies that do not pass the required annual test, must be repaired if possible or replaced.

115 Repairing backflow preventers involves cleaning debris/deposits, replacing worn parts and diagnosing the backflow preventers condition.

116 Here are two Reduced Pressure Principle Assemblies in Parallel

117 A Hersey FRPII

118 Both check valves removed

119 Notice the debris and deposits

120 The #1 check valve on the right has a thicker spring than the #2 check valve

121 Sometimes the check rubber can be cleaned

122 Lots of deposits in this relief valve

123 No wonder the relief valve did not open properly

124 Flushing after cleaning

125 Eventually the water cleans it out

126

127 Closing it up, this valve passed the test after a thorough cleaning and with no parts replaced.

128 Notes: Backflow Prevention Theory and Practice, Center for Training, Research and Education for Environmental Occupations Division of Continuing Education University of Florida TREEO Center