ANSI Z21.22-1999/CSA 4.4-M99 (R2014)

1.1 Scope 1.1.1 This standard applies to the following types of relief valves constructed entirely of new, unused parts and materials: (a) Temperature relief valves and combination temperature and pressure relief valves for use on storage tanks of hot water supp ly systems without heater input limitation T&P valves, hereinafter called. (b) Valves having only pressure relief features for use on storage tanks of hot water supply systems without heater input limitation. (c) Vacuum relief valves. 1.1.2 A temperature relief valve, or a T&P valve shall operate when the temperature sensing element is at 210°F (99°C) or less. A device with a higher operating temperature is not acceptable under this Standard. 1.1.3 A vacuum relief valve shall be of a single-purpose type. 1.1.4 All references to psi throughout this standard are to be considered gage pressures unless otherwise specified. 1.1.5 Exhibit A contains provisions that are unique to Canada.