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

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 supply 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.