WAC 296-826-40020
WAC 296-826-40020. Nonrefrigerated systems
(1) You must make sure piping on nonrefrigerated systems is:
(a) ASTM A-53-2004 Electrical Resistance Welded and Electric Flash Welded Pipe or equal.
(b) At least schedule 80 when joints are threaded.
(c) At least schedule 40 when joints are either welded or welded and flanged.
(2) You must prohibit the use of piping or tubing made of any of the following:
(a) Brass;
(b) Copper;
(c) Galvanized steel.