IPC SECTION 406
AUTOMATIC CLOTHES WASHERS
406.3 Waste connection. The waste from an automatic clothes washer shall discharge through an air break into a standpipe in accordance with Section 802.4 or into a laundry sink. The trap and fixture drain for an automatic clothes washer standpipe shall be a minimum of 2 inches (51 mm) in diameter. The automatic clothes washer fixture drain shall connect to a branch drain or drainage stack a minimum of 3 inches (76 mm) in diameter.
Standpipes shall be individually trapped. Standpipes shall extend a minimum of 18 inches (457mm) and a maximum of 42 inches (1066mm) above the trap. Access shall be provided to all standpipe traps and drains for rodding. No P-trap for a washing machine standpipe shall be installed below the floor.