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Backflow Prevention DevicesField's Fire Protection, Inc. performs annual or semi-annual (depending on local Authority Having Jurisdication requirements) testing of all types of backflow prevention devices. Backflow Prevention Devices in the News: Water in focus for Earth Day Source: American Water Works Association Streamlines staff 04/22/09 Today is Earth Day, and water issues are front and center. Last night, the PBS news show Frontline aired “Poisoned Waters,” a documentary examining how runoff from industry and agriculture is making its way into waterways, and in some cases, drinking water. Sunday, the Associate Press distributed an article on pharmaceuticals from manufacturing operations are ending up in US streams. AWWA maintains information on the issue of pharmaceuticals in water supplies and endocrine disruptors for water professionals and for consumers. Meanwhile, the New York Times tackled the issue of water infrastructure last weekend, noting the stiff competition for the federal stimulus funds for drinking water. “When the state of Ohio asked for suggestions on spending its stimulus money, mayors and city managers put in some 1,400 requests for drinking water projects costing a total of $3 billion," said Melissa Fazekas, a spokeswoman for the Ohio Environmental Protection Agency. Many environmental organizations and water and wastewater utilities are using Earth Day to promote water conservation and cleanup. In Washington, D.C., one group is sponsoring the cleanup of the Anacostia River. The US Environmental Protection Agency headquarters is hosting a festival with exhibits, hands-on experiments and demonstrations. The agency has launched an interactive Earth Day Web site with tips for using water wisely. The US Department of Agriculture used the occasion by announcing that 56 communities in 34 states will receive $144.3 million in loans and grants for infrastructure improvements to improve water availability and quality. The White House, meanwhile, launched an Earth Day blog detailing federal government actions to celebrate Earth Day. In Canada, the Earth Day Canada organization cautioned consumers to be wise about the differences "beteeen green products and green marketing campains," in promoting its Red Flags for Greenwashing campaign. Environment Canada Minister Jim Prentice suggested numerous ways Canadians can "take action," including protecting the quality of the nation's water resources. Earth Day events stretch into next weekend. For example, the Southern Nevada Water Authority is partnering with a local nature park and a manufacturer to showcase water-efficient toilets, which will be sold at a discount, on Saturday as part of “What on Earth Day,” Meanwhile, other organizations like Water For People and the earthdaynetwork are using Earth Day to promote access to safe water in developing countries.
Backflow: You may have heard of it, and you may understand some of what it involves. Backflow is the undesirable reversal of the flow of water or mixtures of water and other undesirable substances from any source (such as used water, industrial fluids, gasses, or any substance other than the intended potable water) into the distribution pipes of the potable water system. There are two types of backflow conditions: backpressure and backsiphonage.
Backpressure: Occurs when the user system is at a higher pressure than the supply water systems allowing undesirable substances to be “pushed” back into the potable water system. Some causes are: booster pumps, potable water system connections for boilers, interconnection with other piping systems operating at higher pressures, or higher elevations in user systems such as highrise buildings.
One specific example of this would be a steam heating system with the make-up water line piped directly into the boiler. The higher pressure in the boiler could force the chemically treated boiler water back through the make-up water line and into the potable water system.
Backsiphonage: Occurs when negative or reduced pressure exists in the supply piping allowing undesirable substances to be “drawn” into the potable water supply. Some causes are:
Undersized supply piping, supply line breaks, reduced supply system pressure on the suction side of an on-line booster pump, or sudden upstream high demand. An example of this is a child drinking milk with a straw. The child “sucks” on the straw and the milk flows up the straw and into the child’s mouth. What the child is actually doing is creating a sub-atmospheric pressure in his mouth and the atmospheric pressure (14.7psia at sea level) is pushing down on the surface of the milk and forcing the milk up the straw and into the child’s mouth.
There is one other very important term that must be understood before we can proceed.
The term is “Cross-Connection,” and it is defined as any actual or potential connection between a potable water system and any other source or system through which it is possible to introduce into the potable system any used water, industrial fluid, gas, or other substance other than the intended potable water with which the system is supplied. By-pass arrangements, jumper connections, removable sections, swivel or change-over devices and other permanent or temporary devices through which, or because of which, backflow can or may occur are considered to be cross-connections.
There are several different types of mechanical backflow prevention devices. An alternative to a mechanical device, is a physical separation, or air gap. The air gap is a physical break in the system. The different types, of mechanical devices, are used in different situations (if there is backpressure or back-siphonage) and for different degrees of hazard. The degree of hazard is based on the fluid (or other substance) that may backflow into the supply piping system. The fluid may be toxic or nontoxic and could create a “non-health” or “health” hazard. A non-health (non-toxic) hazard cross-connection is any point on a water supply system where a polluting substance may come in contact with potable water aesthetically affecting the taste, odor or appearance of the water, but not hazardous to health. A health hazard (toxic) cross-connection is any point on a water supply system where a contaminating substance may come in contact with potable water creating an actual health hazard, causing sickness or death.
Frequently Asked Backflow Questions
What is backflow prevention? Backflow prevention refers to the stoppage of an unwanted reverse flow of water from a potentially polluted source into the drinking water supply. Backflow prevention valves are installed in all water systems to prevent the chance of contaminated water finding its way back into the water system. Under Government legislation, these valves require annual testing by certified tradespeople. Domestic, commercial and industrial customers need to be aware of their responsibilities to prevent backflow. Properly designed and installed plumbing systems will ensure protection. You can improve protection by installing and maintaining backflow prevention devices. When does backflow occur? Backflow occurs because a condition exists in a water supply system that will cause back-siphonage or back-pressure. Back-siphonage can occur on a property through a vacuum created in the water supply system. An example of back-siphonage would be a pipeline breakage, undersized pipework or high withdrawal rates. Back-pressure can occur within properties when high pressure is generated downstream by pumps, thermal expansion or elevation What are typical applications for Double Check Valve Assemblies? May be used where the degree of hazard is low, meaning that the non-potable source is polluted rather than contaminated. What factors can cause a backpressure 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. Where is a Double Check Valve Assembly used? It may be used as protection of all direct connections through which foreign material might enter the potable system in concentration which would constitute a nuisance or aesthetically objectionable, such as air, steam, food, or other material which does not constitute a health hazard. Why is there concern over the contamination of safe drinking water by connection to a fire protection system?Water from a fireline system can backflow into the drinking water system. Fire protection systems are most commonly constructed of uncoated black iron pipe which is considered by plumbing officials to be unacceptable as water system piping material.
Double Check Valve Assembly (DC)
The double check valve assembly (DC) is composed of two single, independently acting check valves. The unit also has two tightly closing, resilient seated, shutoff valves located at each end of the device and four test cocks for the testing of the check valves.
Reduced Pressure Principal Assembly (RP)
Commonly referred to as an RP or RPP, this device consists of two independently acting check valves, together with an automatically operating pressure differential relief valve located between the two check valves. The first check valve reduces the supply pressure at a predetermined amount so that during normal flow, and at cessation of normal flow the pressure between the two check valves shall be lower than the supply pressure. If either check valve leaks, the relief valve will discharge to atmosphere. This will maintain the pressure in the zone between the two check valves lower than the supply pressure. The unit also has two, resilient seated, shutoff valves (one upstream and one downstream of the checks) and properly located test cocks for field testing.
Pressure Vacuum Breaker (PVB)
The pressure vacuum breaker (PVB) is a device that contains within a single body, a single loaded check valve and a loaded air opening valve which opens to admit air whenever the pressure within the body of the device approaches atmospheric. The device has two tight closing, resilient seated, shut-off valves, and it is fitted with test cocks, appropriately placed, for testing the device.
Dual Check Valve (DuC)
The dual check (DuC) is a device which has two single, independent acting check valves in series. It does not have any test-cocks and is generally not field tested.
Dual Check with Atmospheric Port (DCAP)
This device has two independent acting check valves with a relief valve located between the checks. The device is not testable and should only be used for lower degrees of hazard.
Atmospheric Vacuum Breaker (AVB)
An atmospheric vacuum breaker (AVB) is a device which has a moving element inside, which during flow prevents water from spilling from the device and during cessation of flow, drops down to provide a vent opening. This device should not remain under pressure for long durations, and it cannot have any shutoff valve downstream of it.
Air Gap
An air gap is a physical separation between the free flowing discharge end of a potable pipe line and an open or non-pressure receiving vessel. To have an acceptable air gap, the end of the discharge pipe has to be at least twice the diameter of the pipe above the topmost rim of the receiving vessel, but in no case can this distance be less than one inch. This may seem to be the simplest, most effective and least expensive type of protection. However, the chance for future cross-connections the cost of additional pumps to pressurize the system often makes this an expensive protection system.
Standard Testing Procedures for Backflow Preventers
Per Enviromental Protection Agency http://www.epa.gov/OGWDW/crossconnectioncontrol/pdfs/chapter05.pdf
Prior to initiating a test of any backflow device, it is recommended that the following procedures be followed:
1. Permission be obtained from the owner, or his representative, to shut down the water supply. This is necessary to insure that since all testing is accomplished under no-flow conditions, the owner is aware that his water supply will be temporarily shut off while the testing is being performed. Some commercial and industrial operations require constant and uninterrupted water supplies for cooling, boiler feed, seal pump water, etc. and water service interruption cannot be tolerated. The water supply to hospitals and continuous process industries cannot be shut off without planned and coordinated shut downs. The request to shut down the water supply is therefore a necessary prerequisite to protect the customer as well as limit the liability of the tester. Concurrent with the request for permission to shut off the water, it is advisable to point out to the owner, or his representative, that while the water is shut off during the test period, any inadvertent use of water within the building will reduce the water pressure to zero. Backsiphonage could result if unprotected cross-connections existed which would contaminate the building water supply system. In order to address this situation, it is recommended that the owner caution the inhabitants of the building not to use the water until the backflow test is completed and the water pressure restored. Additional options available to the building owner would be the installation of two backflow devices in parallel that would enable a protected bypass flow around the device to be tested. Also, if all water outlets are protected within the building with “fixture outlet protection” backflow devices, cross-connections would not create a problem in the event of potential backsiphonage conditions occurring while devices are tested, or for any other reason.
2. Determine the type of device to be tested i.e., double check valve or reduced pressure principle device.
3. Determine the flow direction. (Reference directional flow arrows or wording provided by the manufacturer on the device.) 4. Number the test cocks, bleed them of potential debris, and assemble appropriate test cock adapters and bushings that may be required. 5. Shut off the downstream (number 2) shut-off valve. (Ref. Item (1) above.)
6. Wait several moments prior to hooking up the test kit hoses when testing a reduced pressure principle device. If water exits the relief valve, in all likelihood, the first check valve is fouled and it is impractical to proceed with the testing until the valve is serviced. This waiting period is not necessary when testing double check valves.
7. Hook up the test kit hoses in the manner appropriate to the device being tested and the specific test being performed. Test personnel are cautioned to be aware and follow local municipal, county, and state testing requirements and guidelines as may be dictated by local authority. The following test procedures are guidelines for standard, generally acceptable test procedures but may be amended, superceded, or modified by local jurisdiction. Test Equipment For field testing of reduced pressure principle backflow preventers and double check valve assemblies, a differential pressure test gauge is utilized having a 0 to 15 psi range and a working pressure of 500 psi. Appropriate length of hoses with necessary fittings accompany the test gauge. Several manufactured test kits are commercially available that incorporate the differential gauge, hoses, and fittings and are packaged for ease of portability and come with protective enclosures or straps for hanging. Calibrated water columns are commercially available that are portable and come with carrying cases. It is important that all test equipment be periodically checked for calibration. Pressure Vacuum Breaker Field testing of a pressure vacuum breaker involves testing both the internal spring loaded soft seated check valve as well as testing the spring loaded air inlet valve. The testing must be performed with the device pressurized and the air inlet closed. The number 2 shut-off valve must also be closed and the air inlet valve canopy removed.
Method 1 Using a differential pressure gauge
Test 1 Test the internal check valve for tightness of 1 psid in the direction of flow. 1. With the valve body under pressure, (number 2 shut-off valve closed and number 1 shut-off valve open) bleed test cocks number 1 and number 2. 2. Hook up the high pressure hose to number 1 test cock and the low pressure hose to number 2 test cock. 3. Bleed the high pressure hose, and low pressure hose, in that order, and close the test kit needle valves slowly. 4. Record the differential pressure on the gauge. A reading of 1 psid is acceptable to insure a tight check valve.
Test 2 Test the air inlet valve for a breakaway of 1 psi. 1. Connect the high pressure hose to test cock number 2, and bleed the high pressure hose. 2. Shut off number 1 shut-off valve. 3. Slowly open the bleed valve of the test kit, and observe and record the psi when the air inlet poppet opens. This should be a minimum of 1 psi. Restore the valve to normal service. Method 2 Using a water column sight tube and 90 degree elbow fitting with bleed needle
Test 1 Test the internal check valve for tightness of 1 psid in the direction of flow. 1. Assemble sight tube to test cock number 1. Open test cock and fill the tube to a minimum of 36-inches of water height. 2. Close number 1 shut-off valve. 3. Open test cock number 2. The air inlet valve should open and discharge water through number 2 test cock. 4. Open number 1 test cock. The sight tube level of water should drop slowly until it stabilizes. This point should be a minimum of 28-inches of water column which equals 1 psi.
Test 2 Test the air inlet valve for a breakaway of 1 psi. 1. Assemble sight tube to test cock number 2. Open test cock number 2 and fill the tube to a minimum of 36-inches of water height. 2. Close number 1 shut-off valve. 3. Bleed water slowly from the number 2 test cock bleed needle and observe the water column height as it drops. 4. At the point when the air inlet valve pops open, record the height of the water column. This point should be a minimum of 28-inches of water column which equals 1 psi. Restore the valve to normal service. Reduced Pressure Backflow Field testing of a reduced pressure principle backflow preventer is accomplished utilizing a differential pressure gauge. The device is tested for three optional characteristics: i.e., (1) The first check valve is tight and maintains a minimum of 5 psi differential pressure, (2) The second check valve is tight against backpressure and (3) The relief valve opens at a minimum of 2 psi below inlet supply pressure. Testing is performed as follows:
Step 1 Test to insure that the first check valve is tight and maintains a minimum pressure of 5 psi differential pressure. 1. Verify that number 1 shut-off valve is open. Close number 2 shut-off valve. If there is no drainage from the relief valve, it is assumed that the first check is tight. 2. Close all test kit valves. 3. Connect the high pressure hose to test cock number 2. 4. Connect the low pressure hose to test cock number 3. 5. Open test cocks number 2 and number 3. 6. Open high side bleed needle valve on test kit bleeding the air from the high hose. Close the high side bleed needle valve. 7. Open the low side bleed needle valve on test kit bleeding air from the low hose. Close the low side bleed needle valve. Record the differential gauge pressure. It should be a minimum of 5 psid. Step 2 Test to insure that the second check is tight against backpressure. 1. Leaving the hoses hooked up as in the conclusion of Step 1 above, connect the bypass hose to test cock number 4. 2. Open test cock number 4, the high control needle valve and the bypass hose control needle valve on the test kit. (This supplies high pressure water downstream of check valve number 2.) If the differential pressure gauge falls off and water comes out of the relief valve, the second check is recorded as leaking. If the differential pressure gauge remains steady, and no water comes out of the relief valve, the second check valve is considered tight 3. To check the tightness of number 2 shut-off valve, leave the hoses hooked up the same as at the conclusion of Step 2 above, and then close test cock number 2. This stops the supply of any high pressure water downstream of check valve number 2. If the differential pressure gauge reading holds steady, the number 2 shut-off valve is recorded as being tight. If the differential pressure gauge drops to zero, the number 2 shut-off valve is recorded as leaking. With a leaking number 2 shut-off valve, the device is, in most cases, in a flow condition and the previous readings taken are invalid. Unless a non-flow condition can be achieved, either through the operation of an additional shut-off downstream, or the use of a temporary compensating bypass hose, accurate test results will not be achieved.
Step 3 To check that the relief valve opens at a minimum pressure of 2 psi below inlet pressure. 1. With the hoses hooked up the same as at the conclusion of Step #2 (3) above, slowly open up the low control needle valve on the test kit and record the differential pressure gauge reading at the point when the water initially starts to drip from the relief valve opening. This pressure reading should not be below 2 psid. This completes the standard field test for a reduced pressure principle backflow preventer. Before removal of the test equipment, the tester should insure that he opens number 2 shut-off valve thereby reestablishing flow. Also, the test kit should be thoroughly drained of all water to prevent freezing by opening all control needle valves and bleed needle valves. All test data should be recorded on appropriate forms. Double Check Valve Assemblies Some field test procedures for testing double check valve assemblies require that the number 1 shut-off valve be closed to accomplish the test. This procedure may introduce debris such as rust and tuberculin into the valve that will impact against check valve number 1 or number 2 and compromise the sealing quality. This potential problem should be considered prior to the selection of the appropriate test method. Two test methods, one requiring closing of the number 1 shut-off valve, and one without this requirement are presented below:
Method 1 Utilizing the differential pressure gauge and not shutting off number 1 shut-off valve.
Step 1 checking check valve number 1 1. Verify that the number 1 shut-off is open. Shut off number 2 shut-off valve. 2. Connect the high hose to test cock number 2. 3. Connect the low hose to test cock number 3. 4. Open test cocks 2 and 3. 5. Open high side bleed needle valve on test kit bleeding the air from the high hose. Close the high side bleed needle valve. 6. Open low side bleed needle valve on test kit bleeding the air from the low hose. Close the low side bleed needle valve. 7. Record the differential gauge pressure reading. It should be a minimum of 1 psid. 8. Disconnect the hoses.
Step 2 Checking check valve number 2. 1. Connect the high hose to test cock number 3. 2. Connect the low hose to test cock number 4. 3. Open test cocks number 3 and 4. 4. Open high side bleed needle valve on test kit bleeding the air from the high hose. Close the high side bleed needle valve. 5. Open low side bleed needle valve on test kit bleeding the air from the low hose. Close the low side bleed needle valve. 6. Record the differential gauge pressure reading. It should be a minimum of 1 psid. 7. Disconnect the hoses. To check tightness of number 2 shut-off valve, both the check valves must be tight and holding a minimum of 1 psid. Also, little or no fluctuation of inlet supply pressure can be tolerated. The testing is performed as follows: 1. Connect the high hose to number 2 test cock. 2. Connect the low hose to number 3 test cock. 3. Connect the bypass hose to number 4 test cock. 4. Open test cocks numbers 2, 3, and 4. 5. Open high side bleed needle valve on test kit bleeding the air from the high hose. Close the high side bleed needle valve. 6. Open low side bleed needle valve on test kit bleeding the air from the low hose. Close the low side bleed needle valve. 7. The differential gauge pressure should read a minimum of 1 psid. 8. Open the high side control needle valve and the bypass hose control needle valve on the test kit. (This supplies high pressure water downstream of check valve number 2). 9. Close test cock number 2. (This stops the supply of any high pressure water downstream of number 2 check valve), If the differential pressure gauge holds steady, the number 2 shut-off valve is recorded as being tight. If the differential pressure gauge drops to zero, the number 2 shut-off valve is recorded as leaking. With a leaking number 2 shut-off valve, the device is, in most cases, in a flow condition, and the previous test readings taken are invalid. Unless a non-flow condition can be achieved, either through the operation of an additional shut-off downstream, or the use of a temporary compensating bypass hose, accurate test results will not be achieved. This completes the standard field test for a double check valve assembly. Prior to removal of the test equipment, the tester should insure that he opens number 2 shut-off valve thereby reestablishing flow. All test data should be recorded on appropriate forms and the test kit drained of water. Method 2 Utilizing “Duplex Gauge” or individual bourdon gauges, requires closing number 1 shut-off.
Step 1 checking check valve number 1 1. Connect the high hose to test cock number 2. 2. Connect the low hose to test cock number 3. 3. Open test cocks number 2 and number 3. 4. Close number 2 shut-off valve; then close number 1 shut-off valve. 5. By means of the high side needle valve, lower the pressure at test cock number 2 about 2 psi below the pressure at test cock number 3. If this small difference can be maintained, then check valve number 1 is reported as “tight”. Proceed to Step number 2. If the small difference cannot be maintained, proceed to Step number 3. Step 2 checking check valve number 2. Proceed exactly the same test procedure as in Step number 1, except that the high hose is connected to test cock number 3 and the low hose connected to test cock number 4.
Step 3 1. Open shut-off valve number 1 to re-pressurize the assembly. 2. Loosely attach the bypass hose to test cock number 1, and bleed from the gauge through the bypass hose by opening the low side needle valve to eliminate trapped air. Close low side needle valve. Tighten bypass hose. Open test cock number 1. 3. Close number 1 shut-off valve. 4. By loosening the low side hose at test cock number 3, lower the pressure in the assembly about 10 psi below normal line conditions. 5. Simultaneously open both needle valves. If the check valve is holding tight the high pressure gauge will begin to drop while the low pressure gauge will increase. Close needle valves. If the gauge shows that a small (no more than 5 psi) backpressure is created and held, then the check valve is reported as tight. If the check valve leaks, a pressure differential is not maintained as both gauges tend to equalize or move back towards each other, then the check valve is reported as leaking. With both needle valves open enough to keep the needles on the gauge stationary, the amount of leakage is visible as the discharge from the upstream needle valve.
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