AIR GAP (AG) Low Hazard High Hazard

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1 AIR GAP (AG) On Low Hazard and High Hazard applications, Air Gap (AG) is used for the physical separation (vertical distance) between the lowest opening point from any pipe or outlet supplying water and the flood level rim of the non-pressurized receiving vessel or receptacle. An example is a kitchen sink - water cannot flow from the sink to the tap in normal circumstances, even if the water supply loses pressure. Air Gaps are very effective, whether it s because of back-siphonage or backpressure, the backflow condition is being isolated. An acceptable AG must be twice the size in diameter of the supply pipe, but never less than one inch, measured vertically above the receiving vessel. Air Gaps must be rigidly mounted and the discharge end of the supply pipe must not be threaded or provided with a means for making connections. Using AG provides clear vertical separation between the pressurized supply pipe and a non-pressurized receiving vessel.

2 Hose Connection Vacuum Breaker Everyday things you do when using an outdoor faucet can put you and your family at risk. If an outdoor faucet is in contact (directly or via a hose) with dirty water and there is an unexpected change in pressure, that water can be sucked back into your home s drinking water pipes. Hose connection vacuum breakers are specifically made for portable hoses attached to threaded faucets. Their purpose is to prevent contaminated water from flowing back into drinking water. These devices screw directly to the faucet outlet. They can be used on a wide variety of installations, such as service sinks, hose faucets near a wading pool, laundry tub faucets, etc. Some units are designed for manual draining during freezing conditions. Some are furnished with breakaway set screws as a tamper proof feature. These devices are not intended for operation under continuous pressure.

3 Atmospheric Vacuum Breaker Used on Low Hazard applications like irrigation systems, an atmospheric vacuum breaker (AVB) is a device used to prevent backflow or the reversal of the direction of water against the direction that the system is designed to flow. The usual types of backflow for which a preventive method is employed to prevent are those that contaminate potable water with contaminated water, such as the backflow of a source and the system in a home. In this event, an Atmospheric Vacuum Breaker is used. It resembles a ninety-degree elbow with a hood to allow air to enter the system, filling the vacuum in the event of back-siphonage. The hood is operated by a poppet valve inside the elbow with the pressure holding it up and keeping the hood closed. If the pressure in the water system happens to drop, the poppet valve drops as well, to compensate for the loss of pressure. The hood is raised by the action of the poppet valve. Air is sucked into the pipe by the loss of pressure and the vacuum is filled before back-siphonage can occur. The pressure is neutralized by air, which creates a buffer between the system of potable water and contaminated water. Because of its use of air, a vacuum breaker cannot be placed in an environment where air is contaminated. The air could be sucked into the plumbing system and contaminate the potable water. It may also suck in contaminated ground water. AVB is a non-testable device. AVB must NOT be installed underground. Absolutely no shut-off valves are allowed on the discharge side of the AVB. A minimum of six inches of clearance above all downstream piping of the AVB is required. The AVB shall not be under continuous pressure for more than 12 hours.

4 Anti-Siphon Valve Used on Low Hazard Applications, Anti-siphon valves (ASV) allow water to flow in one direction. For irrigation purposes, ASV prevents water from siphoning back into the water supply line. ASV prevents unsafe water from entering a clean water supply such as through faucets or shower heads. This can be particularly dangerous where a fertilizer injection system is being used through the sprinklers to fertilize the grass. An ASV prevents the water resting in the sprinkler system pipes from being siphoned back into the home where it could be emitted from a faucet and consumed. The AVB is a non-testable device. The anti-siphon valve must NOT be on continuously for more than 12 hours. The ASV must be installed a minimum of 6 above the highest sprinkler head or emitter outlet. The ASV must also be above ground. A box can be used to cover it, but it must be above ground level. An ASV must not be installed upstream of another on/off valve, such as a zone control valve.

5 Pressure Vacuum Breaker A Pressure Vacuum Breaker (PVB) is used on Sprinkler systems. One PVB is required to service an entire system. Control valves can be located downstream from the PVB. PVB s must be installed a minimum of 12 (1 foot) above the highest point of water they serve. PVB s must be tested by a certified Backflow Assembly Tester (BAT) when installed, moved or repaired. PVB s must be tested annually. No chemical or fertilizer may be introduced into an irrigation system equipped with a PVB. No pump or back-pressure is allowed on the downstream side of a PVB.

6 Double Check Valve (DCVA) When used on Low Hazard applications, the Double Check Valve Assembly (DCVA) protects against back-pressure and back-siphonage. The DCVA consists of two independently operating spring loaded check valves. DCVA can be tested. A Double Check Valve Assembly (DCVA) can be used for sprinkler systems. Only one DCVA is required to serve the system. Control valves can be located downstream of the DCVA. DCVA must be tested by a certified Backflow Assembly Tester (BAT) when assembly is installed, moved or repaired. DCVA s must be tested annually. No chemical or fertilizer may be introduced into an irrigation system equipped with a DCVA. The DCVA must be installed with test cocks facing up or to one side. Sufficient drainage must be provided to prevent assembly from being submerged. A sprinkler blow out valve should be installed downstream of the #2 shutoff.

7 Reduced Pressure Backflow Assembly Used on High Hazard applications, 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 during normal flow. 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. RPBA must be installed a minimum 12 (1 foot) above the surrounding ground or floor. If RPBA is installed outdoors, it should be protected and insulated to prevent freezing. If RPBA is installed indoors, it must meet plumbing code. A sprinkler blow out valve should be installed downstream of the #2 shutoff.

8 High Hazards Air gap (AG) and reduced pressure backflow assemblies (RPBA) are acceptable protection for different types of High Hazards. Examples of High Hazard facilities: Beverage bottling plant Car wash Chemical plant Commercial laundry and dry cleaner Premised where reclaimed water and potable water are provided Film processing facility Food processing plant Hospital, medical center, nursing home, veterinary clinic, medical and dental clinic and blood plasma center Premise with separate irrigation system using the purveyor s water supply with chemical addition Laboratories Metal plating industry Mortuary Petroleum processing storage plant Pier and docks Wastewater lift station and pumping station Wastewater treatment plant

9 Low Hazards Double check valve assembly, pressure vacuum breaker assembly and atmospheric vacuum breaker are types of protection for low hazards. Examples of low hazard facilities: Fire systems Sprinkler system All backflow assemblies must be tested annually by a State certified backflow assembly tester (BAT) after install, repair or replacement. A copy of the test report must be provided to the City of Ephrata Water Department.