Centennial Community Matters: The Water We Use Twice? Understanding Centennial’s Graywater Decision

It is drinking water, irrigation water, snowpack, reservoir storage, water rights, household expense and, increasingly, a question of how thoughtfully we use every gallon available to us.

That is why something called graywater has landed on the Centennial City Council agenda, and why a seemingly technical ordinance deserves a little translation into everyday Centennial English.

First, what exactly is graywater?

Graywater is water that has already been used once inside a home or building but may still be suitable for another non-drinking purpose.

Think about the water leaving a shower, bathtub, bathroom sink or washing machine. Under Colorado's definition, those can be graywater sources. Water from toilets, kitchen sinks and dishwashers is specifically excluded.

With an appropriately designed system, graywater can potentially be reused for purposes such as subsurface landscape irrigation or toilet flushing, depending on the type of system and treatment involved. (US EPA)

In other words, instead of using fresh drinking-quality water for every job in the house, some water can occasionally be asked to work a second shift.

Why is Centennial considering this now?

Colorado changed the rules.

House Bill 24-1362, which took effect January 1, 2026, moved Colorado toward statewide authorization of graywater systems. Rather than requiring each community to specifically opt in, local governments now have the ability to opt out if they do not want graywater treatment systems and uses within their jurisdictions.

Centennial is now considering exactly that.

Ordinance No. 2026-O-15 would opt the City out of the state graywater program and prohibit graywater treatment works and graywater use within Centennial. The ordinance received its first reading September 1, with a public hearing and second reading scheduled for September 15.

Residents can review the City's official information here: Centennial City Council Legal Notices

The interesting part: Centennial has considered the possibilities before

This isn't the City's first conversation about graywater.

In Centennial planning materials from 2025, graywater was identified as something the City could explore through resident surveys, workshops and conversations with developers and water providers. Those materials also noted that graywater, particularly in new development, has the potential to reduce demand for potable water. 

Now the City is considering opting out instead.

That doesn't automatically make the proposed ordinance anti-conservation, nor does supporting graywater automatically make a system simple, inexpensive or appropriate everywhere. Graywater involves plumbing, treatment standards, public-health safeguards and coordination with water providers. Colorado's Division of Water Resources also notes that graywater use remains subject to water-rights requirements, well-permit conditions and water-supplier restrictions. (Division of Water Resources)

And that is where this becomes a Community Matters conversation rather than merely a plumbing conversation.

What should Centennial residents be asking?

The bigger question may not be, Is graywater good or bad?

A better question is: What role should water reuse play in Centennial's long-term approach to conservation?

Residents might reasonably want to know whether the administrative and infrastructure challenges outweigh the amount of water that could realistically be conserved here. They might also ask whether Centennial should prohibit graywater entirely, allow limited categories, encourage future pilot projects, or revisit the issue as technology and building practices evolve.

Colorado law allows local governments that opt out to reconsider later, so a prohibition today does not necessarily close the door forever.

That distinction matters.

A gallon worth thinking about

Most of us turn on a faucet without thinking about the remarkable chain of snow, reservoirs, treatment systems, pipes, infrastructure and people required to make clean water appear.

Graywater asks a different question:

Once we've used that water, are we finished with it?

Centennial City Council is deciding what the City's answer should be, at least for now.

And in a state where water shapes nearly everything around us, that is a conversation worth bringing out of the municipal code and around the community table. 💧