1、AN AMERICAN NATIONAL STANDARD ASME A112.1.2-2012(Revision of ASME A112.1.2-2004)Air Gaps in Plumbing Systems (For Plumbing Fixtures and Water-Connected Receptors)ASME A112.1.2-2012(Revision of ASME A112.1.2-2004)Air Gaps in PlumbingSystems (For PlumbingFixtures andWater-ConnectedReceptors)AN AMERICA
2、N NATIONAL STANDARDThree Park Avenue New York, NY 10016 USADate of Issuance: April 9, 2012This Standard will be revised when the Society approves the issuance of a new edition.ASME issues written replies to inquiries concerning interpretations of technical aspects of thisStandard. Periodically certa
3、in actions of the ASME A112 Committee may be published as Cases.Cases and interpretations are published on the ASME Web site under the Committee Pages athttp:/cstools.asme.org/ as they are issued.Errata to codes and standards may be posted on the ASME Web site under the Committee Pages toprovide cor
4、rections to incorrectly published items, or to correct typographical or grammatical errorsin codes and standards. Such errata shall be used on the date posted.The Committee Pages can be found at http:/cstools.asme.org/. There is an option available toautomatically receive an e-mail notification when
5、 errata are posted to a particular code or standard.This option can be found on the appropriate Committee Page after selecting “Errata” in the “PublicationInformation” section.ASME is the registered trademark of The American Society of Mechanical Engineers.This code or standard was developed under p
6、rocedures accredited as meeting the criteria for American NationalStandards. The Standards Committee that approved the code or standard was balanced to assure that individuals fromcompetent and concerned interests have had an opportunity to participate. The proposed code or standard was madeavailabl
7、e for public review and comment that provides an opportunity for additional public input from industry, academia,regulatory agencies, and the public-at-large.ASME does not “approve,” “rate,” or “endorse” any item, construction, proprietary device, or activity.ASME does not take any position with res
8、pect to the validity of any patent rights asserted in connection with anyitems mentioned in this document, and does not undertake to insure anyone utilizing a standard against liability forinfringement of any applicable letters patent, nor assumes any such liability. Users of a code or standard are
9、expresslyadvised that determination of the validity of any such patent rights, and the risk of infringement of such rights, isentirely their own responsibility.Participation by federal agency representative(s) or person(s) affiliated with industry is not to be interpreted asgovernment or industry en
10、dorsement of this code or standard.ASME accepts responsibility for only those interpretations of this document issued in accordance with the establishedASME procedures and policies, which precludes the issuance of interpretations by individuals.No part of this document may be reproduced in any form,
11、in an electronic retrieval system or otherwise,without the prior written permission of the publisher.The American Society of Mechanical EngineersThree Park Avenue, New York, NY 10016-5990Copyright 2012 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.CONTENTSForeword
12、 ivCommittee Roster vCorrespondence With the A112 Committee . vi1 General 12 Requirements . 3Figures1 Example of Air Gap and Effective Opening . 22 Example of Near-Wall Influence on Air Gap 33 Example of Near-Wall Influences on Air Gap: Top View . 5Table1 Minimum Air Gaps for Generally Used Plumbing
13、 Fixtures 4iiiFOREWORDThe Sectional Committee on Minimum Requirements for Plumbing and Standardization ofPlumbing Equipment, A40, realizing the need for regulations and devices to protect the purityof water supplies in buildings, organized a technical subcommittee on air gaps and backflowpreventers
14、in 1938. This subgroup completed a tentative draft of a proposed standard for airgaps for a meeting of Subcommittee 12 on January 20, 1939.The draft proposal was considered and revised. Copies of this revised report were distributedto interested firms and individuals in industry for further criticis
15、m and comment. At the Octobermeeting of the subcommittee, the comments received were carefully considered. The April 1940draft, which followed shortly, was distributed to the members of Sectional Committee A40 fordiscussion. Certain changes were recommended, as well as the addition of two sections c
16、overingwater inlets to tanks having overflows and drinking fountain bubblers. These were incorporatedin the revised draft dated May 1940. Copies of this draft were distributed to the members of thesectional committee and to a group of more than 100 health supervisory officials, plumbinginspectors, s
17、tate plumbing associations, and others. The received recommendations promptedanother revision, which was reviewed by the members of Subcommittee 12. The changes andrefinements made were incorporated, and a final revision dated July 1941 was approved by letterballot vote of the sectional committee.Fo
18、llowing approval by the sectional committee and the sponsor organizations, the draft wastransmitted to the American Standards Association (now known as the American NationalStandards Institute) for approval and designation as an American Standard. This designationwas given in January 1942.In 1958, t
19、he functions of Sectional Committee A40 pertaining to Standards for PlumbingEquipment were transferred to Standards Committee A112, and this Standard on Air Gaps inPlumbing Systems was assigned to Panel I. Panel I recommended the Standards reaffirmationon April 18, 1972. Standards Committee A112 con
20、curred in this recommendation on June 28,1972. The American National Standards Institute approved this reaffirmation on January 23, 1973and designated it A112.1.2-1973. The document was reaffirmed in 1989, revised in 1990, andrevised again in 2004.ThisStandard isbased ontheapplication ofcertain phys
21、icalprinciplesto thedesign ofplumbingfixtures and other water-connected devices and their installation in plumbing systems. It hasbeen prepared to avoid complicated measurements and tests, to determine proper air gaps bysimple measurements to be made in the field, to provide an adequate margin of sa
22、fety overlaboratory tests, and to simplify inspections and the preparation of definite regulations. It alsowas prepared to prevent all types of backflow conditions where or when the insertion of a suitableair gap is appropriate.This revision eliminates Nonmandatory Appendix A, which did not offer eq
23、uivalent backflowprotection to the requirements of this Standard.It is recognized that, in some cases, the air gap is not practical and other types of backflowpreventers would give adequate protection.This Standard was developed with the intent that due consideration be given to the adoptionof these
24、 provisions by model, state, and local codes.Suggestions for improvement of this Standard are welcome. They should be sent toThe American Society of Mechanical Engineers, Attn: Secretary, A112 Main Committee,Three Park Avenue, New York, NY 10016-5990.This Standard was approved as an American Nationa
25、l Standard on March 5, 2012.ivASME A112 COMMITTEEStandardization ofPlumbing Materials and Equipment(The following is the roster of the Committee at the time of approval of this Standard.)STANDARDS COMMITTEE OFFICERSW. M. Smith, ChairD. W. Viola, Vice ChairF. Constantino, SecretarySTANDARDS COMMITTEE
26、 PERSONNELR. H. Ackroyd, Rand Technical ConsultingS. R. Aridi, NSF InternationalD. Orton, Alternate, NSF InternationalJ. A. Ballanco, JB Engineering however, they shouldnot contain proprietary names or information.Requests that are not in this format will be rewritten in this format by the Committee
27、 priorto being answered, which may inadvertently change the intent of the original request.ASME procedures provide for reconsideration of any interpretation when or if additionalinformation that might affect an interpretation is available. Further, persons aggrieved by aninterpretation may appeal to
28、 the cognizant ASME Committee or Subcommittee. ASME does not“approve,” “certify,” “rate,” or “endorse” any item, construction, proprietary device, or activity.Attending Committee Meetings. The A112 Standards Committee schedules meetings as needed,which are open to the public. Persons wishing to atte
29、nd any meeting should contact the Secretaryof the A112 Standards Committee. The A112 home page, http:/go.asme.org/A112committee,contains information on future meeting dates and locations.viASME A112.1.2-2012AIR GAPS IN PLUMBING SYSTEMS (FOR PLUMBINGFIXTURES AND WATER-CONNECTED RECEPTORS)1 GENERAL1.1
30、 ScopeThis 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 MeasurementThe values stated in either SI (Metric) or inch/pound
31、unitsareto beregardedasthestandard.In thisStandard,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 nonconforman
32、ce withthis Standard. All references to gallons are toU.S. gallons.1.3 ReferencesThe 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 Soci
33、ety of Sanitary Engineering(ASSE), 901 Canterbury Road, Westlake, OH 44145(www.asse-plumbing.org)CSA B125.3, Plumbing FittingsPublisher: Canadian Standards Association (CSA), 5060Spectrum Way, Mississauga, Ontario L4W 5N6, Can-ada (www.csa.ca)1.4 Definitionsair gap: a vertical distance through the a
34、tmospherebetween 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).1May also be
35、 obtained from American National StandardsInstitute (ANSI), 25 West 43rd Street, New York, NY 10036.1air 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
36、(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 wallThe minimum required air gap shall be measuredverti
37、cally 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
38、-phonage and backpressure are types of backflow.backflow connection or condition: any arrangementwhereby backflow can occur.backflow prevention device: adeviceorassembly(combina-tion of devices) designed to prevent backflow.critical level: the level at which backsiphonage will notoccur, including an
39、y required factor of safety.critical level mark: the manufacturers 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 o
40、f 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
41、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 gaprelated term applied to drinkingfountain nozzles.flood-level rim: the top edge of the receptor from whichwater will flow out of the receptor (an overflow openingis
42、not considered a flood-level rim).ASME A112.1.2-2012Fig. 1 Example of Air Gap and Effective OpeningBFAXFlood-level rimof fixtureThe case when effective(minimum) opening isthrough the seatA = air gap distanceB = effective opening;diameter for a circularpassageway or the diameter of an areaequivalent
43、to a noncircular passagewayF = diameter of watersupply dischargeX = inside diameter of thesupply pipe, controlvalve inlet2ASME A112.1.2-2012Fig. 2 Example of Near-Wall Influence on Air GapCAFlood-level rim of fixtureSide wallA p air gap distanceC p 3H11547 the effective openingNOTE: The definition o
44、f “flood-level rim” is based on a fixtureor receptor with reasonably level edges. It is recognized that certainfixtures or receptors may be provided with uneven edges. In suchcases, the equivalent of flood-level rim shall be considered as themaximum water elevation possible with full flow of water f
45、romall water-supplied pipes discharging into the fixture or receptor.Obviously, in such cases, the flood-level rim or its equivalent isnot capable of simple measurement in the field.free area: the area created between a near wall and thefaucet or fitting when the distance between the walland the out
46、let of the faucet or device is three times thediameter of the effective opening for a single wall or adistance four times the diameter of the effective openingfor two intersecting walls.2 REQUIREMENTS2.1 Minimum Required Air Gap for General UseThe following requirements of minimum required airgaps s
47、hall apply to plumbing fixtures in general use. Itis recognized that the actual water level in a receptormay rise higher than the flood-level rim and a factor ofsafety has been applied to compensate for this higherlevel.(a) The minimum required air gap shall be twice thediameter of the effective ope
48、ning, but in no case lessthan the values specified in Table 1 or in conformancewith the performance requirements of paras. 2.4.1 and2.4.2.3(b) These minimum requirements may not apply tocertain unusual conditions. When a receptor receiveswater from two or more outlets of different sizes, airgaps for
49、 all water supply openings shall be at least equalto that required for the largest opening.2.2 Water Closet TanksRequirements for backsiphonage protection in gravitywater closet tanks shall be in accordance withASSE/ANSI 1002 or CSA B125.3.2.3 Minimum Elevation of Drinking FountainNozzles2Drinking fountain nozzles, including those that mayat times extend through a water surface and with anorifice diameter not greater than an 11-mm (0.440-in.)or 97-mm2(0.150-in.2) area, shall be placed so that thelower edge of the nozzle orifice is at an elevation notless than 19 mm (0.75 in.) abov
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