Commerce City, CO Water Use Rules: Recycled Water Rules (2026)

Commerce City Revised Municipal Code § 5-4201 amends the 2021 International Residential Code to add a set of graywater reuse provisions. Section P2901.2.3 requires that graywater used for toilet flushing be dyed with blue or green food grade vegetable dye so it is visibly distinct from potable water, and Section P2901.2.1 requires nonpotable outlets, such as hose bibs and open pipes, to carry a warning sign at least a half-inch tall reading that the water is nonpotable. Section P2902.5.6 requires the potable water connection to any graywater system to be protected against backflow by an air gap or a reduced-pressure-principle backflow prevention assembly, and Section P2910.1 separately requires a double check valve immediately downstream of the water service shutoff for any nonpotable reuse system.

Where graywater is used to flush toilets or urinals, Section P2910.2.2 requires filtration through a 100-micron or finer filter, though reclaimed water sources and properly treated graywater systems under Section P2911.6.1 are excepted from the added filtration step. Storage tanks must be built of durable, nonabsorbent, corrosion-resistant material compatible with the system's disinfection chemicals under Section P2910.9.3, though a tank isn't required at all where the reuse is limited to subsurface irrigation into a mulch basin sized at three times the anticipated daily flow. Sections P2911.1.1 through P2911.1.4 require the collection, toilet-flushing, dispersed-irrigation and mulch-basin systems each to follow the code's own reference figures, and Section P2911.7.4 requires every storage tank to carry a trapped overflow line to the sanitary sewer with no shutoff valve on it.