(1) Except as provided in Sentence (2), the size of every fixture outlet pipe shall conform to Table 7.4.9.3.
(2) The part of the fixture outlet pipe that is common to three compartments of a sink shall be one size larger than the largest fixture outlet pipe of the compartments that it serves.
(3) Where clothes washers do not drain to a laundry tray, the trap inlet shall be fitted with a vertical standpipe that is not less than 600 mm long measured from the trap weir and the top of the standpipe shall terminate above the flood level rim of the clothes washer it serves.