ASME A112.1.2 pdf free download

ASME A112.1.2 pdf free download Air Gaps in Plumbing Systems (For Plumbing Fixtures and Water-Connected Receptors)
1 GENERAL
1.1 Scope This Standard identifies methods of providing protec- tion against backsiphonage through means of an air gap and establishes physical requirements and methods of testing air gaps for plumbing fixtures and water receptors.
1.2 Units of Measurement The values stated in either SI (Metric) or inch/pound units are to be regarded as the standard. In this Standard, the inch/pound units are shown in parentheses. The values stated in each measurement system are equiva- lent in application; however, each system is to be used independently. Combining values from the two mea- surement systems can result in nonconformance with this Standard. All references to gallons are to U.S. gallons.
1.3 References The following documents form a part of this Standard to the extent specified herein. Unless otherwise speci- fied, the latest edition shall apply. ASSE/ANSI 1002, Water-Closet Flush Tank Ball Cocks 1 Publisher: American Society of Sanitary Engineering (ASSE), 901 Canterbury Road, Westlake, OH 44145 (www.asse-plumbing.org) CSA B125.3, Plumbing Fittings Publisher: Canadian Standards Association (CSA), 5060 Spectrum Way, Mississauga, Ontario L4W 5N6, Can- ada (www.csa.ca)
1.4 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 backsiphon- age under laboratory conditions, with still water, wide-open control valve, and a vacuum of at least 635 mm Hg (25 in. 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 backsiphonage 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 (a) the size of the effective opening (b) 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 point of the faucet, spout, or supply pipe to the flood-level rim of the fixture or receptor (see Figs. 1 and 2). backflow: the flow of water or other liquids into the distributing pipes of a potable supply of water from any source or sources other than the intended source. Backsi- phonage and backpressure 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: the level at which backsiphonage will not occur, including any required factor of safety. critical level mark: the manufacturer’s designated critical level. 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-sectional areas of the individual lines or the area of the outlet, whichever is smaller. NOTE: To illustrate the practical use of the term “effective open- ing,” refer to Fig. 1.
With ordinary plumbing supply fittings, the minimum cross-sectional area usually occurs at the seat of the control valve, B; but, in other cases, it may be at the point of discharge (spout) or at the inlet to the control valve, X. elevation: the air gap–related term applied to drinking fountain nozzles. flood-level rim: the top edge of the receptor from which water will flow out of the receptor (an overflow opening is not considered a flood-level rim).
NOTE: The definition of “flood-level rim” is based on a fixture or receptor with reasonably level edges. It is recognized that certain fixtures or receptors may be provided with uneven edges. In such cases, the equivalent of flood-level rim shall be considered as the maximum water elevation possible with full flow of water from all water-supplied pipes discharging into the fixture or receptor. Obviously, in such cases, the flood-level rim or its equivalent is not capable of simple measurement in the field. free area: the area created between a near wall and the faucet or fitting when the distance between the wall and the outlet of the faucet or device is three times the diameter of the effective opening for a single wall or a distance four times the diameter ofthe effective opening for two intersecting walls.