ASME A112.1.2 pdf download Air Gaps in Plumbing Systems (For Plumbing Fixtures and Water-Connected Receptors)
This Standard identifies methods of providing protec-tion against backsiphonage through means of an air gapand establishes physical requirements and methods oftesting air gaps for plumbing fixtures and waterreceptors.
1.2 Units of Measurement
The values stated in either SI (Metric) or inch/poundunits are to be regarded as the standard.In this Standard,the inch/ pound units are shown in parentheses.Thevalues stated in each measurement system are equiva-lent in application; however, each system is to be usedindependently. Combining values from the two mea-surement systems can result in nonconformance withthis Standard. All references to gallons are toU.s. gallons.
The following documents form a part of this Standardto the extent specified herein. Unless otherwise speci-fied, the latest edition shall apply.
ASSE/ ANSI 1002,Water-Closet Flush Tank Ball Cocks1Publisher: 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),5060Spectrum Way,Mississauga,Ontario L4w 5N6,Can-ada (www.csa.ca)
air gap: a vertical distance through the atmospherebetween the lowest potable water outlet and the highestlevel 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 least635 mm Hg (25 in.Hg).
air gap,minimum required: an air gap greater than thecritical air gap by a factor of safety to cover serviceconditions. The air gap required to prevent backsiphon-age through a water supply opening (faucet or valve),under the action of atmospheric pressure and a vacuumin the water supply system, depends principally on(a) the size of the effective opening
(b)the distance between the end of the supply fittingoutlet (spout) pipe and a nearby wall
The minimum required air gap shall be measuredvertically from the lowest point of the faucet, spout, orsupply pipe to the flood-level rim of the fixture orreceptor (see Figs. 1 and 2).
backflow: the flow of water or other liquids into the dis-tributing pipes of a potable supply of water from anysource or sources other than the intended source.Backsi-phonage and backpressure are types of backflow.
backflow connection or condition: any arrangementwhereby backflow can occur.
backflow prevention device: a device or assembly (combina-tion of devices) designed to prevent backflow.
critical level: the level at which backsiphonage will notoccur,including any required factor of safety.
critical level mark: the manufacturer’s designatedcritical level.
effective opening: the smallest cross-sectional area in afaucet,device,or a supply pipe through which waterflows to an outlet. If two or more lines supply one outlet,the effective opening shall be the sum of thecross-sectional areas of the individual lines or the areaof 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,theminimum cross-sectional area usually occurs at the seat of thecontrol valve,B; but, in other cases, it may be at the point ofdischarge (spout) or at the inlet to the control valve,X.
elevation: the air gap-related term applied to drinkingfountain nozzles.
flood-level rimm: the top edge of the receptor from whichwater will flow out of the receptor (an overflow openingis 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.