Graywater (also spelled gray water, greywater, or grey water) may be defined in different ways. The two most common definitions are: 1) all domestic wastewater except toilet wastes and 2) all wastewater except toilet and kitchen wastes.
Graywater is potentially a source of water that could be reused in such applications as subsurface irrigation or toilet flushing. However, at this time, the reuse of graywater has not been authorized by the Colorado General Assembly. In 2012, legislation was proposed but was not passed.
In Colorado, reclaimed water is wastewater that has been treated and disinfected in a wastewater treatment plant before being used again. Reclaimed water is regulated in Regulation 84 - Reclaimed Water Control Regulation. Link to Reg 84
The current regulations for septic systems, the Individual Sewage Disposal System Guidelines, do provide for a smaller soil treatment area (drainfield) for graywater if the toilet wastes are treated or removed in an alternate system such as a composting toilet or vault. Link to Guidelines
Assuming that graywater reuse will be authorized at some time in the future, some factors that will need to be considered for each situation include:
- Does the water provider allow graywater reuse? The water provider may be a municipal water provider or a private well with permit restrictions from the State Engineer in the Division of Water Resources. Link to State Engineer Office
- Can interior plumbing that allows separation of graywater from other wastes and prevents contamination of the potable (drinking) water and its plumbing system be installed? This may be difficult in a house that is already built.
- What will be done during times the graywater system is not in use such as during vacations or during the winter if the graywater reuse is for irrigation?
- What kind of treatment will the graywater need for the planned use to prevent causing health problems or so that the graywater system will operate with as few problems as possible? Graywater is not clean water but may contain soap, chemicals, germs, etc.
- How will graywater use impact the wastewater system? In locations where an on-site wastewater treatment system (OWTS) is used, the remaining wastewater after the graywater is removed may be concentrated such that it will cause operating problems for the OWTS.
Other regulations that may apply:
- Plumbing Codes
- Building Codes
- At a site where graywater treatment is greater than 2,000 gpd, the graywater treatment system is considered a domestic wastewater treatment works and the system must be approved by the Water Quality Control Division through site location and design approval process, covered by Regulation 22 - Site Location and Design Approval Regulations for Domestic Wastewater Treatment Works. More information for the site location and design approval process is available at: Link to Design Review page.
- The Division of Natural Resources has an Administrative Position paper on graywater reuse available at: Link to DNR paper.