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ASME A112.1.2-2004 pdf download

ASME A112.1.2-2004 pdf download.Air Gaps in Plumbing Systems (For Plumbing Fixtures and Water-Connected Receptors)
1.5 Definitions air gap: a vertical distance through the atmosphere between the lowest potable water outlet and the highest level of the source of fluid contamination. air gap, critical: the air gap that will prevent back siphon- age when tested under laboratory conditions, with still water, wide-open control valve, and a vacuum of at least 25 in. Hg (635 mm Hg). air gap, minimum required: an air gap greater than the critical air gap by a factor of safety to cover service conditions. The air gap required to prevent back siphon- age through a water supply opening (faucet or valve), under the action of atmospheric pressure and a vacuum in the water supply system, depends principally on the size of the effective opening and the distance between the end of the supply fitting outlet (spout) pipe and a nearby wall. The minimum required air gap shall be measured vertically from the lowest part of the outlet of the faucet, spout, or supply pipe to the flood-level rim of the fixture or receptor (see Figs. 1, 2, and A-1). backflow: the flow of water or other liquids into the dis- tributing pipes of a potable supply of water from any source or sources other than the intended source. Back siphonage and back pressure are types of backflow. backflow connection or condition: any arrangement whereby backflow can occur. backflow prevention device: a device orassembly (combina- tion of devices) designed to prevent backflow. critical level mark: the level at which back siphonage will not occur, including any required factor of safety; a permanent mark on the external surface of the faucet or device that is visible after installation of the faucet or device. When the faucet or device is installed with the critical level mark at or above the flood-level rim of a fixture or receptor, this creates the minimum required air gap and will prevent back siphonage. effective opening: the smallest cross-sectional area in a faucet, device, or a supply pipe through which water flows to an outlet. Iftwo or more lines supply one outlet, the effective opening shall be the sum of the cross-sec- tional areas of the individual lines or the area of the outlet, whichever is smaller.
2.4 Determination of Minimum Air Gaps for Plumbing Systems The following is the procedure for the determination of minimum air gaps for plumbing systems: (a) Install the faucet or device, with all checking mem- bers upstream of the air gap removed or held fully open, in its normally installed position in a container [approxi- mately 15 in. (380 mm) 01 6 )mm 052( .ni؋ .ni؋ (150 mm) deep]. The outlet of the faucet or device shall have atleast a free area offour times its effective opening between the container and the outlet. The mounting surface of the faucet or device shall be level or plumb with the water surface in the container. (b) Connect the inlet(s) of the faucet or device to a vacuum source. The vacuum shall be measured at the inlet of the faucet or device. (c) A means to change the water level in the container relative to the outlet of the faucet or device shall be provided. (d) Start the test with the water level at the mounting surface of the faucet or device. (e) Withthe faucetordevice fullyopenfrom its inlet(s) to the point of discharge to the atmosphere, apply a vacuum of 25 in. Hg (635 mm Hg) to the inlet(s). Back siphonage under these conditions is cause for rejection of the faucet or device. (f) The water level shall slowly be brought closer to the discharge outlet of the faucet or device until back siphonage occurs. At this point, record the water level. The vertical distance between the water level and the lowest point on the discharge outlet of the faucet or device shall be measured and recorded.

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