(1) Except as provided in Sentence (2), a Class 1 sewage system shall be designed to receive only human body waste for disposal.
(2) Where the sewage system is specifically designed for the biological decomposition of non-waterborne biodegradable kitchen wastes or requires the addition of small quantities of plant matter to improve the decomposition of human body waste, it may receive such wastes in addition to human body waste.
(3) Where the sewage system is designed with a drain for the removal of excess liquid, then the sewage system shall drain to a Class 3, 4, or 5 sewage system.