Tap water in Denver is compliant with the US Environmental Protection Agency guidelines for healthy drinking water. It consistently ranks as a city with some of the cleanest water in the United States.
However, this does not mean that Denver tap water is entirely free of contaminants.
Denver Water Quality Report: What is in the Water?
The top contaminants in Denver tap water are Haloacetic acids (HAA5 and HAA9) and trihalomethanes (TTHMs), which may potentially be cancerous. However, these contaminants fall below the legal limit set by the EPA.
A common concern of Denver residents is the presence of Cryptosporidium (crypto) and giardia from byproducts of infected animals in the Rocky Mountain region. However, testing has not found traces of these parasites in the drinking water.
There may be trace amounts of lead detected in your tap water, though this does not come from the water itself. Lead leaches into water via pipes and fixtures in older residences and privately owned properties.
Buildings constructed before 1951 may have higher traces of lead due to lead water service lines. Consider checking the piping, solders, faucets, and fixtures in your residence. Fixtures produced before 2014 will likely not meet EPA guidelines and may cause higher lead levels in your tap water.
Denver’s tap water is classified as “soft to moderately hard.”
Hardness in water is caused by compounds of calcium, magnesium, and other metal sediments. The USGS classifies soft water as anything below 60 milligrams of metals per liter and hard water as anything between 121 to 180 mg/L.
Denver Water, the largest water treatment center, has two collection points. The southern collection point is listed as “moderately hard,” with 75 to 120 mg/L. Its northern collection point is listed as “soft” water and measures 40 to 50 mg/L.
Because Denver’s tap water is sourced entirely from surface water, it tends to be softer than groundwater. The quick movement of surface water usually prevents most minerals from dissolving into the water.
However, the surface water may become “harder” in winter, as waterways and reservoirs freeze and allow water to absorb more minerals.
While there are no health risks to consuming hard water, it can be a source of household nuisance and inconvenience. You may notice chalky residue on cleaned dishes, difficulty in creating suds when washing your hair and hands, as well as a slight mineral aftertaste.
If have a water softening system, ensure that it is well maintained so that no residues from this additional filtration system are added to your water.
Denver’s water is 100% sourced from surface water. Surface water is water from snowmelt that has accumulated in rivers, streams, creeks, lakes, and reservoirs.
The primary source of Denver’s surface water is the Rocky Mountains.
This water then passes through three primary filtration and treatment plants that serve the residents of Denver and some surrounding suburbs: the Denver Water Board (1.4 million residents), the North Washington Street Water & Sanitation District (34,000 residents), and the Crestview WSD (18,000 residents).
Surface water from Rocky Mountains travels along the Colorado River to residents as far south as southern California. Denver is the first and closest stop. That allows the city to collect this fresh snowmelt before it travels across the ground and picks up added sediment and contaminants.
As a result, Denver has some of the freshest and cleanest water, even prior to the filtration and disinfection processes.
Although water from the Rocky Mountains is generally clean, all water is filtered through treatment centers before it is ultimately distributed to homes and businesses.
The Denver Water Board has explained the process in detail:
- Coagulation or flocculation: In this first step, the “raw,” untreated water is collected in large basins. Alum, a non-toxic liquid, and polymer substances are added into the water and cause solid sediments to stick together in large clumps.
- Sedimentation: As they grow larger, these clumps grow heavier and sink to the bottom of the basin. Once they do, these fragments get separated from the water.
- Filtration: The water is then filtered through fine layers of granulated materials to remove any smaller particles remaining in the water. Depending on the treatment center, these layers are made of either sand or coal. The result is clear, sediment-free water.
- Disinfection: After the sediment has been removed, a disinfectant is added to the water to treat bacteria, viruses, and any other remaining microbes.
- Corrosion control: Overly acidic water may react with the metal distribution systems and plumbing. Alkaline substances are added to the water to maintain a pH to reduce corrosion as the water moves.
- Distribution: Finally, the water is sent underground to reservoirs and through the distribution systems. These lead the water to homes and businesses.
Denver is considered one of the cities with the cleanest water in the United States. While there is much contention over the first place spot, Denver is consistently listed in the top ranks.
Cities that regularly compete with Denver for cleanest (and best-tasting) tap water are Louisville, Kentucky, with water filtered from the Ohio River, and New York City, with water from reservoirs in the Catskill Mountains. Chicago tap water is also one of the cleanest.
Residents regularly drink Denver tap water. However, water filters for pitchers and faucets (along with home filtration systems) are growing in popularity.
These filters are used to remove any contaminants that might have entered your tap water en route from the water treatment center to your home. Depending on the type of filter, they can remove chlorine, unwanted minerals, bacteria, and even lead.