What is graywater?

    In Colorado, graywater and its uses are defined by Colorado state law: 

    • Graywater is the water used in a residential, commercial or industrial building that is collected after the first use and put to a second use. 
    • Graywater can only be collected from bathroom and laundry room sinks, bathtubs, showers and laundry machines.  
    • Graywater is not wastewater from toilets, urinals, kitchen sinks, dishwashers and non-laundry utility sinks. This flow cannot be captured and must continue to the wastewater collection system.   
    • If authorized by the local city or county, a limited amount of graywater can be used for certain indoor uses (like toilet and urinal flushing) and subsurface (below ground) irrigation of non-agricultural plants. Due to Fort Collins water rights, reuse can only be considered for toilet flushing.  
    • Additional information can be found here.

    Can I currently use graywater in Fort Collins?

    Graywater cannot currently be used in Fort Collins except in limited research settings. However, City staff is working on developing a proposed graywater ordinance that would authorize certain graywater uses.

    When will graywater be authorized in Fort Collins and when can I install a system?

    Before graywater can be used in Fort Collins, the Fort Collins City Council must enact an ordinance authorizing graywater. The current schedule, to bring the proposed graywater ordinance to City Council, is on August 16, 2022, for first reading. The proposed ordinance would need to be approved again on a second reading and would go into effect after that. Once effective, residents would need to apply for a permit if they want to use graywater.

    Why is the City considering graywater now?

    City Council recently prioritized creating an ordinance to allow graywater. In addition, achieving greater water efficiency, with measures such as graywater, is supported by numerous plans, such as:

    • Colorado Water Plan (2015) sets a goal to achieve 400,000 acre-feet of conservation in the municipal and industrial sectors by 2050. 
    • Fort Collins Utilities Water Efficiency Plan (2015) sets a goal to reduce average water use to 130 gallons per capita per day by 2030. This requires an additional 8% reduction from the current 5-year average over the next eight years.
    • City Plan (2019) points to encouraging greater efficiency in new and redevelopment.

    Fort Collins is looking to allow and implement, where legally feasible and safe, greater water efficiency measures. One measure includes the concept of using the right type of water for the right use. The City has already implemented raw (untreated) water for park irrigation and the state allows limited rain barrel use. While much of the water used in Fort Collins is treated to drinking water standards, not all of it needs to be. Allowing raw water and reuse from graywater for uses that don’t require drinking water level water quality, helps improve efficiency, supply and demand challenges, and avoids the energy use associated with unnecessarily treating water.

    Will graywater be mandatory in Fort Collins?

    No. If approved, the graywater program would be optional.

    What types of graywater uses is the City considering?

    The graywater ordinance City staff is currently developing would allow graywater to be used for toilet and urinal flushing only. Graywater would not be authorized in Fort Collins for other uses like subsurface irrigation. This is due to water rights limitations that apply to the water service providers in Fort Collins. The limitations dictate how Colorado-Big Thompson (CBT) Project water from Horsetooth Reservoir can be used. If these limitations change in the future, City staff may consider amendments to the ordinance.

    A graywater ordinance ultimately must conform with the water rights of the given community. Each community has different water providers with different water rights portfolios, which dictate the ability and extent to which they can authorize the use of graywater.  

    Northern Water operates the CBT Project, which encompasses Horsetooth Reservoir. About half of Fort Collins Utilities’ water comes from Horsetooth. CBT water is not reusable, but the Northern Water Board passed a resolution allowing use of CBT for only non-consumptive graywater uses, which is defined in the resolution as only toilet and urinal flushing. This puts Fort Collins Utilities at a disadvantage with graywater compared to other communities who have significant sources of reusable water supplies, such as Denver Water.

    What types of developments are being considered for graywater?

    All types of new developments and redevelopment – single-family and multi-family residential and commercial.

    Where is graywater being considered for use?

    Without approval by the other water providers who service properties within Fort Collins City Limits – East Larimer County Water District, Fort Collins-Loveland Water District, and West Fort Collins Water District – graywater, if approved, will be limited to Fort Collins Utilities water service area (serves about 75% of the City Limits). City Staff are currently working with the other water providers to determine whether they will consent to graywater use within their service areas, within City Limits.

    Is graywater safe to use?

    The Colorado Department of Public Health & Environment has rules (Regulation 86) for graywater use and development. City and county graywater ordinances must conform with these rules to ensure the public’s safety. In accordance with these rules, graywater must pass through a tank that provides partial treatment (not to the level of drinking water standards) before it can be reused for indoor toilet flushing.

    What is the current financial cost/benefit to developing a graywater system?

    The table below provides estimates from limited information available on the cost to install a graywater system in Colorado and the water savings associated with graywater use. More empirical data is needed to improve confidence in these estimates. However, it is evident that there is a greater financial benefit from scaling up graywater systems. Single-family homes have a limited amount of graywater. Large facilities that use more water, such as hotels, recreation centers, multi-family residential and dormitories, could realize more significant cost and water savings from graywater. There are many variables that impact the cost and savings, making graywater more affordable, with a greater return on investment (ROI). 

    Cost: The cost to develop a graywater system is significant. This is due, in part, to the Colorado Department of Public Health & Environment’s rules. Future changes to those rules could potentially reduce the cost to install graywater, by requiring less expensive treatment systems.

    Savings: Graywater use reduces the amount of water and wastewater charged on a utility bill each month, by using wastewater to flush toilets and discharging less water to wastewater systems. In addition, if water and wastewater rates increase over time, the savings estimates may increase.

    Estimated costs and benefits across selected water conservation measures 



    Estimated Costs 

    Estimated Benefits 




    Average upfront cost to customer or developer 

    Average annual maintenance costs 

    Average annual water savings 

    Average annual utility bill savings 

    Return on investment for customer 

    Single-family homes

    (4 residents)

    Graywater (toilet flushing only) 



    10,000-20,000 gallons 


    33-65 years 


    (100 residents) 

    Graywater (toilet flushing only) 



    230,000-500,000 gallons 


    30-65 years

    Assumptions in this table: 

    • The maintenance costs for the graywater measures are very rough estimates and may likely be too low.  
    • All utility bill savings and ROI are based on the 2022 Fort Collins Utilities water and wastewater rates and do not include maintenance costs.  
    • For reference, a single-family home in the Fort Collins Utilities service area with four residents is estimated to use an average of 130,000 gallons per year. 
    • The graywater values above assume the system is in a new construction setting. It is far more costly to retrofit existing structures than to incorporate a system into new construction. The existing limited data suggest more interest will take place in new development. 

    Why should I consider graywater?

    For larger water uses, graywater may make economic sense, but there may be other reasons to consider graywater beyond the cost savings. For some, the environmental benefits of minimizing the energy that goes into treating water and the more efficient use of water resources is incentivizing on its own and can represent a commitment to conservation and sustainable water use.  

    Would I need a permit for graywater?

    Yes. City of Fort Collins Building Services would provide a permit for graywater systems, which would require plans and inspection. The cost and other permit details will be determined closer to Council review of the ordinance, currently slated for summer 2022.

    Where is graywater currently allowed in Colorado?

    Four areas on Colorado’s Front Range have adopted graywater regulations. Two others are actively exploring a graywater ordinance. The early adopters are communities with a significant portion of reusable water supplies in their portfolios. The Colorado Graywater Comparisons table below summarizes information on the agencies that have adopted graywater regulations in Colorado based on publicly available information and 2021 interviews with staff from each entity.

    Colorado Graywater Comparisons 



    Systems Permitted 




    Denver City & County 



    Sustainability Goals 

    3 homes  

    Denver Water paid for installation 

    Town of Castle Rock 



    Development community 

    29 homes 

    Reduced Water Impact Fees 

    Pitkin County 



    Sustainability goals 


    City of Golden  


    Subsurface Irrigation 

    Sustainability goals 

    Plans for direct install pilot 




    Community interest 



    Under development. 

    Larimer County 

    Planned for 2022.