Is Denver Tap Water Safe to Drink in 2023?

Denver's tap water complies with the US Environmental Protection Agency (EPA) guidelines for healthy drinking water and is consistently ranked as the cleanest in the US.

However, this doesn’t mean that the water is entirely free of contaminants. Hazardous contaminants like lead, chromium, haloacetic acids, and barium are all present in Denver’s water, albeit in trace amounts.

In this guide, we break down the results from Denver’s 2024 water quality report to tell you everything you need to know about the safety of its tap water.

Denver Water Quality Report: What's in the Water?

Although Denver’s tap water is considered safe to drink by the authorities, the 2024 water quality report shows the presence of copper, chromium, nitrate, barium, and fluoride. While the levels of these contaminants are well below the limit set by the EPA, it’s still best to learn what dangers they pose and how to eliminate them.

What is perhaps slightly more concerning is that the same report has also found the presence of lead in Denver’s water. Since the EPA asserts that there’s no safe level of lead in drinking water, this is an issue that should be dealt with.

Another 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.

Fortunately, Denver’s drinking water has no trace of other dangerous contaminants like arsenic, mercury, or uranium.

A Table of Contaminants for the Denver Tap Water in 2024

Below is a table that lists the concentrations of the most dangerous contaminants found in Denver’s water and how they fare against the EPA regulations.

Note: These results are from the 2024 water quality report which relates to the water quality for the previous year, 2023.

Lead and Copper in Denver Water

Reports show that Denver tap water contains copper, but the levels are not alarming. There are only 60 parts per billion (ppb) of copper in Denver’s drinking water, which is quite safe considering that the EPA standard is 1,300 ppb.

However, the same can’t be said for the lead presence in Denver’s tap water. Denver tap water contains 4.5 ppb of lead. As the EPA establishes, there should be no lead in the water (even in trace amounts) as it can cause a plethora of health concerns varying in severity—from stomach issues and constipation to memory loss and nervous system damage.

We should also note that the lead does not come from the water supply itself. The presence of lead in the city’s water comes from lead pipes and fixtures in older residences and some privately owned properties built prior to 1986.

Buildings constructed before 1986 may have higher traces of lead and copper because these metals were commonly used in the construction of water supply lines. Consider checking your residence's piping, solders, faucets, and fixtures for corrosion. Fixtures produced before 2014 will likely not meet EPA guidelines (as this was when the EPA started enforcing regulations) and may cause higher lead levels in tap water.

The good news is that Denver authorities are running a Lead Reduction Program to eliminate this issue.

Haloacetic Acids and Total Trihalomethanes (TTHMs)

Other contaminants found in Denver’s tap water that might be a cause for concern are haloacetic acids (HAA5) and total trihalomethanes (TTHMs), as both may be potentially cancerous. HAA5 is naturally occurring and quite common in public water systems all across the USA, but it has been linked to bladder cancer. TTHMs are a byproduct of chlorine, which is a chemical used to sanitize public water systems.

Although trace amounts were found in Denver’s water supply, these contaminants fall within the legal limit set by the EPA. The EPA standard for HAA5 is 60 ppb, and there’s only 16.2 ppb of HAA5 in Denver’s water. The reported TTHM levels aren’t worrying either, as the 28.9 ppb amount is safely below the 80 ppb standard set by the EPA.

Nitrate, Barium, and Fluoride

Nitrate, barium, and fluoride can be found anywhere on Earth in natural deposits, and when these deposits erode over time, they can easily leach into the surface water. That’s the case in Denver, too.

In addition to natural erosion, nitrate can find its way into the water supply through runoff from septic tanks and systems, while barium can enter water sources via drilling waste. Fluoride, on the other hand, is intentionally added to drinking water to improve dental health, but it may also enter water supplies via waste dumps from aluminum and fertilizer factories.

If the levels of these elements in drinking water are too high, they become a serious health concern. Nitrate is well-known as a quite powerful poison. Barium, when consumed in large doses, can cause paralysis and even death. High levels of fluoride in drinking water can result in arthritis.

That being said, Denver residents have nothing to fear about any of these contaminants as they’re far below the EPA’s safe thresholds.

Is Denver Tap Water Hard or Soft?

Denver’s tap water is classified as “soft to moderately hard.” Hardness in water is caused by compounds of calcium, magnesium, and other mineral sediments. The USGS classifies soft water as anything below 60 milligrams of hardness per liter and hard water as anything between 121 to 180mg/L. As of November 2023, Denver’s tap water had 80 mg/L of hardness.

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, surface water may become “harder” in winter as waterways and reservoirs freeze, allowing the water to absorb more minerals.

While consuming hard water does not pose health risks, it can be a source of inconvenience. You may notice chalky residue on cleaned dishes, difficulty creating suds when washing your hair and hands, and a slight mineral aftertaste.

If you’re unsure about your water hardness level, we recommend you send your water sample to a certified water testing lab like Simplelab Technologies.

Where Does Denver Get Its 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 three filtration and treatment plants include 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 the Rocky Mountains travels along the Colorado River to residents as far south as southern California. Denver is the first and closest stop. This allows the city to collect the water that comes from freshly melted snow 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 before the filtration and disinfection processes.

How is Tap Water Treated in Denver?

Although water from the Rocky Mountains is generally clean, all water is filtered through treatment centers before it’s distributed to homes and businesses.

The Denver Water Board has explained the process in detail:

1. 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 to the water and cause solid sediments to stick together in large clumps.

2. 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.

3. 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.

4. Disinfection: After the sediment has been removed, a disinfectant is added to the water to treat bacteria, viruses, and any other remaining microbes.

5. 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.

6. Distribution: Finally, the water is sent underground to reservoirs and through the distribution systems. These lead the water to homes and businesses.

Does Denver Have the Cleanest Tap Water?

Denver has some of the cleanest water in the United States. While there is much contention over which city takes first place, Denver is consistently listed at the top.

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.

Do People Drink Tap Water in Denver?

Residents regularly drink Denver’s 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 the 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.

Final Thoughts

Denver’s tap water is safe to drink since all the hazardous contaminants are well below the health standards set by the EPA. The only exception is lead, but this leaches into the drinking water via eroding old pipes, solders, and fixtures.

To eliminate the potential health risks caused by this dangerous heavy metal, you may want to consider installing water filters or purchasing water pitchers that can effectively remove it.