Mont. Code Ann. § 75-5-325
Definitions
75-5-325 . Definitions. As used in this part, unless the context indicates otherwise, the following definitions apply:
(1) "Gray water" means wastewater that is collected separately from a sewage flow and that does not contain industrial chemicals, hazardous wastes, or wastewater from toilets.
(2) "Gray water reuse system" means a plumbing system that collects gray water.