Preface: This is the eighth edition of CSA/ANSI Z21.10.1 • CSA 4.1, Gas water heaters, volume I, storage water heaters with input ratings of 75,000 Btu per hour or less. It supersedes the previous editions published in 2017, 2014, 2013, 2009, 2004, 2001 and 1998. This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group. This Standard has been approved by the American National Standards Institute (ANSI) as an American National Standard. Scope: 1.1 This Standard applies to newly produced, automatic storage water heaters having input ratings of 75,000 Btu/hr (21 980 W) or less (see Clause 3, Definitions), hereinafter referred to as water heaters or appliances, constructed entirely of new, unused parts and materials: a) for use with natural gas; b) for use with manufactured gas; c) for use with mixed gas; d) for use with liquefied petroleum gases; e) for use with LP gas-air mixtures; f) for recreational vehicle installation for use with liquefied petroleum gases only (see Clause 4.1.26); g) for manufactured home (mobile home) installation convertible for use with natural gas and liquefied petroleum gases when provision is made for the simple conversion from one gas to the other (see Clause 4.1.25); h) for recreational vehicle installation convertible for use with natural gas and liquefied petroleum gases when provision is made for the simple conversion from one gas to the other (see Clause 4.1.26); and i) for use with combination potable water/space heating applications (see Clause 4.1.29and Clause 3, Definitions). 1.2 This Standard also applies to water heaters incorporating heat pipe heat exchangers (see Clause 4.4, Heat pipe heat exchangers). 1.3 Direct vent water heaters anticipated by this Standard are essentially balanced flue appliances with the air intake and vent outlet in close proximity. Other designs are to be subjected to such additional tests as believed necessary at the discretion of the testing agency. 1.4 Water heaters for installation in recreational vehicles are to be of the direct vent type. 1.5 This Standard also applies to water heaters with draft hoods which are factory-equipped with automatic vent damper devices (see Clause 3, Definitions), hereinafter referred to as vent damper devices. 1.6 This Standard also applies to water heaters of other than the direct vent type which are factory- equipped with electrically operated or mechanically actuated automatic flue damper devices (see Clause 3, Definitions), hereinafter referred to as flue damper devices. 1.7 If a value for measurement as given in this Standard is followed by an equivalent value in other units, the first stated value is to be regarded as the specification, except as noted in Clauses 4.33.2 and 4.34.2. 1.8 All references to "psi" throughout this Standard are to be considered gauge pressures unless otherwise specified. 1.9 Clause 7, Items unique to the United States, contains provisions that are unique to the United States. 1.10 Clause 8, Items unique to Canada, contains provisions that are unique to Canada. 1.11 Special construction provisions applicable to a water heater designed for use with an optional listed conversion kit are outlined under Annex F, Optional provisions for listed appliance conversion kits. 1.12 Clause 2, Reference publications, contains a list of standards specifically referenced in this Standard, and sources from which these reference standards may be obtained. 1.13 In this Standard, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; and "may" is used to express an option or that which is permissible within the limits of the Standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designed normative (mandatory) or informative (non-mandatory) to define their application.