CONTENTS

Foreword iv

Committee Roster v

Correspondence With the A112 Committee vi

1. General 1

2. Requirements 3

Figures

1. Example of Air Gap and Effective Opening 2

2. Example of Near-Wall Influence on Air Gap 3

3. Example of Near-Wall Influences on Air Gap: Top View 5

Table

1 Minimum Air Gaps for Generally Used Plumbing Fixtures 4

FOREWORD

The Sectional Committee on Minimum Requirements for Plumbing and Standardization of Plumbing Equipment, A40, realizing the need for regulations and devices to protect the purity of water supplies in buildings, organized a technical subcommittee on air gaps and backflow preventers in 1938. This subgroup completed a tentative draft of a proposed standard for air gaps for a meeting of Subcommittee 12 on January 20, 1939.

The draft proposal was considered and revised. Copies of this revised report were distributed to interested firms and individuals in industry for further criticism and comment. At the October meeting of the subcommittee, the comments received were carefully considered. The April 1940 draft, which followed shortly, was distributed to the members of Sectional Committee A40 for discussion. Certain changes were recommended, as well as the addition of two sections covering water inlets to tanks having overflows and drinking fountain bubblers. These were incorporated in the revised draft dated May 1940. Copies of this draft were distributed to the members of the sectional committee and to a group of more than 100 health supervisory officials, plumbing inspectors, state plumbing associations, and others. The received recommendations prompted another revision, which was reviewed by the members of Subcommittee 12. The changes and refinements made were incorporated, and a final revision dated July 1941 was approved by letter ballot vote of the sectional committee.

Following approval by the sectional committee and the sponsor organizations, the draft was transmitted to the American Standards Association (now known as the American National Standards Institute) for approval and designation as an American Standard. This designation was given in January 1942.

In 1958, the functions of Sectional Committee A40 pertaining to Standards for Plumbing Equipment were transferred to Standards Committee A112, and this Standard on Air Gaps in Plumbing Systems was assigned to Panel I. Panel I recommended the Standard’s reaffirmation on April 18, 1972. Standards Committee A112 concurred in this recommendation on June 28, 1972. The American National Standards Institute approved this reaffirmation on January 23, 1973 and designated it A112.1.2-1973. The document was reaffirmed in 1989, revised in 1990, and revised again in 2004.

This Standard is based on the application of certain physical principles to the design of plumbing fixtures and other water-connected devices and their installation in plumbing systems. It has been prepared to avoid complicated measurements and tests, to determine proper air gaps by simple measurements to be made in the field, to provide an adequate margin of safety over laboratory tests, and to simplify inspections and the preparation of definite regulations. It also was prepared to prevent all types of backflow conditions where or when the insertion of a suitable air gap is appropriate.

This revision eliminates Nonmandatory Appendix A, which did not offer equivalent backflow protection to the requirements of this Standard.

It is recognized that, in some cases, the air gap is not practical and other types of backflow preventers would give adequate protection.

This Standard was developed with the intent that due consideration be given to the adoption of these provisions by model, state, and local codes.

Suggestions for improvement of this Standard are welcome. They should be sent to The 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 National Standard on March 5, 2012.

iv

ASME A112 COMMITTEE

Standardization of Plumbing Materials and Equipment

(The following is the roster of the Committee at the time of approval of this Standard.)

STANDARDS COMMITTEE OFFICERS

W. M. Smith, Chair

D. W. Viola, Vice Chair

F. Constantino, Secretary

1. H. Ackroyd, Rand Technical Consulting

2. R. Aridi, NSF International

D. Orton, Alternate, NSF International

STANDARDS COMMITTEE PERSONNEL

D. W. Gallman, Alternate, Bradley Corp.

R. Emmerson, Consultant

L. S. Galowin, Consultant

J. A. Ballanco, JB Engineering & Code Consulting

J. E. Bertrand, Moen, Inc.

1. A. Mercer, Alternate, Moen, Inc.

2. N. Burgess, Burgess Group, Inc.

M. Campos, International Code Council

S. L. Cavanaugh, United Association

W. E. Chapin, Cash Acme

F. Constantino, The American Society of Mechanical Engineers

P. V. DeMarco, International Association of Plumbing and Mechanical Officials

D. E. Holloway, Alternate, International Association of Plumbing and Mechanical Officials

N. E. Dickey, Canadian Standards Association International

C. Caruana, Alternate, Canadian Standards Association International

G. S. Duren, Code Compliance, Inc.

T. R. Eberhardy, Bradley Corp.

R. L. George, Plumb-Tech LLC

R. I. Greenwald, Sunroc Corp.

G. W. Harrison, Wayne Harrison Consulting

S. D. Hazzard, American Society of Sanitary Engineering

J. M. Koeller, Koeller and Co.

N. M. Kummerlen, Consultant

J. W. Lauer, Sloan Valve Co.

T. C. Pitcherello, New Jersey Department of Community Affairs

1. Rawalpindiwala, Kohler Co.

2. J. Stessman, Alternate, Kohler Co.

S. A. Remedios, Delta Faucet Co.

C. Trendelman, Alternate, Delta Faucet Co.

G. L. Simmons, Charlotte Pipe and Foundry Co.

W. B. Morris, Alternate, Charlotte Pipe and Foundry Co.

W. M. Smith, Jay R. Smith Manufacturing Co.

D. W. Viola, International Association of Plumbing and Mechanical Officials

W. C. Whitehead, Whitehead Consulting Services

PROJECT TEAM 1.2 — AIR GAPS

1. H. Ackroyd, Project Team Leader, Rand Technical Consulting

2. F. Asay, Backflow Prevention Institute

J. A. Ballanco, JB Engineering & Code Consulting

1. Campos, International Code Council

2. M. Kummerlen, Consultant

S. A. Remedios, Delta Faucet Co.

P. L. Traylor, Air Gap International

v

CORRESPONDENCE WITH THE A112 COMMITTEE

General. ASME Standards are developed and maintained with the intent to represent the consensus of concerned interests. As such, users of this Standard may interact with the Committee by requesting interpretations, proposing revisions, and attending Committee meetings. Corre- spondence should be addressed to

Secretary, A112 Standards Committee

The American Society of Mechanical Engineers Three Park Avenue

New York, NY 10016-5990

https://go.asme.org/Inquiry

Proposing Revisions. Revisions are made periodically to the Standard to incorporate changes that appear necessary or desirable, as demonstrated by the experience gained from the application of the Standard. Approved revisions will be published periodically.

The Committee welcomes proposals for revisions to this Standard. Such proposals should be as specific as possible, citing the edition, the paragraph number(s), the proposed wording, and a detailed description of the reasons for the proposal, including any pertinent documentation. When appropriate, proposals should be submitted using the A112 Project Initiation Request Form. Proposing a Case. Cases may be issued for the purpose of providing alternative rules when justified, to permit early implementation of an approved revision when the need is urgent, or to provide rules not covered by existing provisions. Cases are effective immediately upon ASME

approval and shall be posted on the ASME Committee Web page.

Requests for Cases shall provide a Statement of Need and Background Information. The request should identify the Standard, the paragraph, figure or table number(s), and be written as a Question and Reply in the same format as existing Cases. Requests for Cases should also indicate the applicable edition(s) of the Standard to which the proposed Case applies.

Interpretations. Upon request, the A112 Committee will render an interpretation of any require- ment of the Standard. Interpretations can only be rendered in response to a written request sent to the Secretary of the A112 Standards Committee.

The request for interpretation should be clear and unambiguous. It is further recommended that the inquirer submit his/her request in the following format:

Subject: Cite the applicable paragraph number(s) and the topic of the inquiry.

Edition: Cite the applicable edition of the Standard for which the interpretation is being requested.

Question: Phrase the question as a request for an interpretation of a specific requirement suitable for general understanding and use, not as a request for an approval of a proprietary design or situation. The inquirer may also include any plans or drawings that are necessary to explain the question; however, they should not contain proprietary names or information.

Requests that are not in this format will be rewritten in this format by the Committee prior to being answered, which may inadvertently change the intent of the original request.

ASME procedures provide for reconsideration of any interpretation when or if additional information that might affect an interpretation is available. Further, persons aggrieved by an interpretation may appeal to 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 attend any meeting should contact the Secretary of the A112 Standards Committee. The A112 home page, https://go.asme.org/A112committee,

contains information on future meeting dates and locations.

vi

ASME A112.1.2-2012

AIR GAPS IN PLUMBING SYSTEMS (FOR PLUMBING FIXTURES AND WATER-CONNECTED RECEPTORS)

1. GENERAL

   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.

      
      

   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.

      
      

   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 Cocks1 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)

      
      

   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).

      
      

      1 May also be obtained from American National Standards Institute (ANSI), 25 West 43rd Street, New York, NY 10036.

      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 backsiphon- 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

      1. the size of the effective opening

      2. 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 dis- tributing 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 or assembly (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. If two 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).

1