PDFWAC 480-66-410
Water closets.
(1) Every flush toilet must have a rim flush bowl or be so constructed as to prevent the accumulation of fecal matter on the bowl. The bowl must be constructed of a smooth finished material impervious to moisture.
(2) Every bowl must be installed in a manner which allows surroundings and floor space to be easily cleaned.
(3) No pan, plunger or wash-out water closets are permitted except that pan or double-pan types are permitted for movable facilities.
(4) Every flush toilet must have a separate hinged seat made of a smooth finished material, other than metal, impervious to moisture.