City Water Systems
Understanding how water is sourced, treated, and delivered to your home through municipal infrastructure.
Understanding Your City Water System Guide
A detailed guide to how municipal water systems work and what it means for your household.
Where Colorado's Water Comes From
Colorado's municipal water draws from two primary sources: surface water (rivers, streams, reservoirs collecting snowmelt) and groundwater (underground aquifers accessed through wells). The Colorado River, South Platte River, and Arkansas River basins serve as critical watersheds.
Approximately 80% of the state's precipitation falls as mountain snow, making the spring snowmelt season critical for reservoir storage. During drought years, utilities draw more heavily on groundwater — but deep aquifers like the Denver Basin system recharge slowly over geological timescales. Many communities blend both sources to balance reliability and quality.
Treatment Process: 6 Steps to Your Tap
Screening
Raw water passes through coarse screens and bar racks that remove branches, leaves, trash, and aquatic vegetation — protecting downstream equipment from damage.
Coagulation & Flocculation
Chemical coagulants (alum or ferric chloride) neutralize charges on fine particles, causing them to clump into larger, heavier aggregations called floc that can settle out by gravity.
Sedimentation
Water flows into large, quiet settling basins where heavy floc sinks to the bottom over several hours. Clarified water is drawn from the top for the next stage.
Filtration
Water passes through layers of sand, anthracite coal, or activated carbon that trap remaining particles and microorganisms. Some plants use sub-micron membrane filtration.
Disinfection
Chlorine or chloramines inactivate bacteria, viruses, and parasites like Giardia. A controlled residual remains in the water to prevent regrowth during distribution.
Corrosion Control
Orthophosphate or pH adjustment forms a protective coating inside metal pipes, reducing lead, copper, and iron from dissolving into the water on its way to your home.
The Distribution Network
Once water leaves the treatment plant, it enters a complex network of pipes, pumps, and storage facilities. This infrastructure — often the largest and most expensive asset a utility owns — delivers treated water at adequate pressure to every connected home, business, and fire hydrant.
- Storage tanks — Fill overnight and release during peak hours, providing emergency reserves for firefighting.
- Booster stations — Push water uphill in Colorado's hilly Front Range terrain to maintain pressure at higher elevations.
- Pressure zones — Divide the system into distinct areas maintained at 40-80 PSI with pressure-reducing valves.
- Hydrant flushing — Routine clearing of sediment that may cause temporary discoloration near flushing operations.
Pipe Materials in Colorado Systems
The standard material for water mains for generations. Strong and durable but susceptible to internal corrosion and tuberculation (rust nodule buildup) that reduces flow capacity and affects water color and taste.
Zinc-coated steel common in residential service lines and indoor plumbing. Over time, the zinc coating wears away, exposing the underlying steel to corrosion — leading to restricted flow, discoloration, and mineral deposit accumulation.
The preferred material for residential plumbing, with good corrosion resistance in most water chemistries. Aggressive or acidic water can cause elevated copper levels, but proper corrosion control treatment by utilities protects copper pipes throughout the system.
Lightweight, corrosion-resistant, and inexpensive. PVC doesn't contribute metals to the water supply but can become brittle over time and is susceptible to damage from ground movement in certain soil conditions.
Lead was used for service lines through the 1950s and in some areas into the 1980s. Utilities across Colorado are actively inventorying and replacing these lines. Corrosion control treatment reduces lead dissolution, but full replacement is the long-term solution.
Why Water Can Change After Treatment
Water leaving the treatment plant meets stringent quality standards, but its characteristics can shift as it travels through miles of pipe. This is normal and reflects physical and chemical realities:
- Corrosion interaction — Metal pipes dissolve low levels of iron, copper, or lead into water over time, especially when water sits overnight.
- Sediment disturbance — Main breaks, hydrant use, or construction can stir settled deposits, causing temporary discoloration.
- Temperature shifts — Warmer water is more chemically reactive, affecting taste and corrosion rates seasonally.
This is why testing at the tap — not just at the treatment plant — provides the most complete picture of what's delivered to your household.
See What Happens Inside Your Plumbing
Your home's plumbing is the last mile of the water system.