(1) All plumbing shall be sized, installed, and maintained in accordance with the Montana State Plumbing Code. No establishment shall have both a potable and non-potable water supply except by specific permission of the department. The potable water system shall be installed in such a manner so as to preclude the possibility of back siphonage. Grease traps shall not be required except in special cases as may be determined by the health authority.

(2) Refrigerators, cooking kettles, and similar types of enclosed equipment in which food, portable equipment, or utensils are placed shall not be directly connected to the drainage system. Each waste pipe from such equipment shall discharge into an open, accessible, individual waste sink, floor drain, or other suitable fixture which is properly trapped and vented. Indirect connections of drain lines from other equipment used in the preparation of food or washing of equipment and utensils may be required by the health authority when, in their opinion, the installation is such that backflow of sewage is likely to occur. Each walk-in refrigerator shall be equipped with a floor drain, so installed as to preclude the backflow of sewage into the refrigerator, or all parts of the floor of each walk-in refrigerator shall be graded to drain to the outside through a wastepipe, doorway, or other opening.

(3) Indirect waste connections shall be provided for drains, overflows, or relief vents from the water supply system.

(4) Drain lines from equipment shall not discharge waste water in such a manner as will permit the flooding of floors or the flowing of water across working or walking areas or into difficult to clean areas, or otherwise create a nuisance.