Where the Rivers Meet: St. Louis Water Quality Explained

Where Does St. Louis Tap Water Come From?

St. Louis tap water is provided by the City of St. Louis Water Division. The source water comes from the Mississippi and Missouri rivers and is collected at one of two treatment plants. The Howard Bend water treatment plant gets its water directly from the Missouri River, while the Chain of Rocks water treatment plant gets its water from the confluence where the two rivers meet.

According to the 2023 Consumer Confidence Report, the City of St. Louis Water Division processes up to 124 million gallons of water per day, ensuring that it meets the safe drinking water standards set by the Environmental Protection Agency (EPA).

The Missouri Department of Natural Resources is responsible for assessing St. Louis’ water sources for susceptibility to viruses, bacteria, algal blooms, volatile organic compounds, nitrates and nitrites, and other contaminants.

The most recent report found that the St. Louis water system is highly susceptible to “invasive aquatic invertebrates such as zebra mussels,” which can “degrade aquatic ecosystems and damage intake infrastructure and pipes.”

It’s also susceptible to giardia and cryptosporidium, primarily from runoff from animal waste, but these pathogens are removed during the water treatment process.

How Is St. Louis Drinking Water Treated?

St. Louis tap water goes through a multistep treatment process that includes:

• Disinfection with chlorine to kill viruses and bacteria
• Precipitation softening, which reduces the hardness of the water
• Flocculation, which causes particles to clump together so they can be removed
• Filtration, which uses a physical filter to remove unwanted contaminants

The treatment process results in high-quality, clean drinking water, with almost no risk of waterborne disease for healthy individuals. However, the chemicals used in the process leave behind disinfection byproducts, which can pose a health risk in large amounts.

The City of St. Louis Water Division regularly tests for more than 150 contaminants, and it releases the concentrations of each contaminant in its annual water quality report.

Why Is the Water Cloudy in St. Louis, Missouri?

Because its water comes from surface water sources, St. Louis water quality can vary throughout the year. Sometimes, usually in winter, it can be milky- or cloudy-looking.

According to the Water Division, this is due to variations in the water temperature, which can range from 33 F to 90 F. When the temperature is low, oxygen from the surrounding air dissolves into the water supply and is released when the temperature rises as the water passes through the distribution system and into your home.

There’s no need to boil the water or buy bottled water: This cloudy water is safe to drink and isn’t an indication of rust or sediment in the water supply. If it bothers you, you can run the tap water until cold water comes out, which is less likely to be cloudy.

What Contaminants Are Found in St. Louis Drinking Water?

St. Louis touts its reputation for good, clean water. In fact, it won an award from the U.S. Conference of Mayors for having the best-tasting water out of more than 90 American cities. But how does it stack up when it comes to common contaminants? Should you feel comfortable drinking St. Louis tap water without a home water filter system?

Although St. Louis water quality meets the guidelines of the EPA, it does contain high levels of some contaminants that may pose health risks in large quantities.

Here are five contaminants of concern that the Environmental Working Group (EWG) has flagged as being present in large quantities in St. Louis tap water:

1. Chromium (hexavalent)

Hexavalent chromium, or chromium-6, is one of two types of chromium sometimes found in drinking water, and it’s the more toxic of the two. At high levels, it can lead to cancer, liver damage, and reproductive harm. The EPA hasn’t set a legal limit for chromium-6, but the state of California set a public health goal of 0.02 parts per billion (ppb).

Chromium levels in St. Louis tap water can be as high as 1.16 ppb, which is 58 times the EWG’s health guideline and California’s public health goal:

• EPA maximum allowance: No legal limit
• EWG recommended maximum: 0.02 ppb
• St. Louis maximum detected level: 1.16 ppb

2. Arsenic

Arsenic needs no introduction: This heavy metal affects the nervous system and other vital organs when it’s ingested in large quantities. As a naturally occurring substance, arsenic often enters surface water and groundwater through natural deposits.

Although arsenic levels in St. Louis tap water are below the legal limit, they exceed the EWG’s recommendation by 109 times:

• EPA maximum allowance: 10 ppb
• EWG recommended maximum: 0.004 ppb
• St. Louis maximum contaminant level: 0.435 ppb

3. Total trihalomethanes (TTHMs)

Trihalomethanes are a group of disinfection byproducts linked to cancer and harm to fetal growth. They include chloroform, bromoform, and two other chemicals, and are collectively referred to as total trihalomethanes (TTHMs).

St. Louis tap water contains 15.3 ppb TTHMs, which is lower than the legal limit but 102 times higher than the EWG’s health recommendation:

• EPA maximum allowance: 80 ppb
• EWG recommended maximum: 0.15 ppb
• St. Louis maximum contaminant level: 15.3 ppb

4. Haloacetic acids (HAA5)

Haloacetic acids (HAA5) are another group of disinfection byproducts formed during the water treatment process. According to the EWG, a concentration of 0.1 ppb represents a “one-in-a-million lifetime cancer risk,” but the EPA’s upper limit is significantly higher, at 60 ppb. St. Louis tap water is within the legal limit but 214 times higher than the EWG’s recommendation:

• EPA maximum allowance: 60 ppb
• EWG recommended maximum: 0.1 ppb
• St. Louis maximum contaminant level: 21.4 ppb

5. Haloacetic acids (HAA9)

HAA5 only includes five haloacetic acids; four more acids bring the total to nine. The HAA9 grouping has no legal limit, but the EWG recommends a maximum of 0.06 ppb in order to reduce the risk of cancer. St. Louis tap water exceeds this limit by 405 times:

• EPA maximum allowance: no legal limit
• EWG recommended maximum: 0.06 ppb
• St. Louis maximum contaminant level: 24.3 ppb

Should You Use a Water Filter to Improve the St. Louis Water Quality?

The tap water in St. Louis is safe to drink when it comes to E. coli, cryptosporidium, and other pathogens. Occasionally, the local water utility will release a boil water advisory if pathogen levels are too high. You can check for advisories at the government website.

As for other contaminants, that’s up to you. Activated carbon filters can remove some disinfection byproducts like chlorine and improve the smell and the taste of your water.

Reverse osmosis systems are more effective at removing heavy metals like lead and arsenic, as well as forever chemicals like perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS).

Check your local water quality report by ZIP code to find out which contaminants are present, or test your tap water to see for yourself. Then choose a filter with an NSF rating that matches the contaminants you want to remove.

Does St. Louis Drinking Water Contain PFAS?

Forever chemicals, also known as per- and polyfluoroalkyl substances or PFAS, are man-made chemicals used in industrial settings, at military sites and airports, and in firefighting foam. If you live in close proximity to areas where PFAS are used, it can increase the likelihood of these forever chemicals getting into your water supply.

According to St. Louis Public Radio, “St. Louis' water has been tested [for PFAS] over the last decade and was found to be safe, but the EPA’s new rules are stricter.” Some water systems in Missouri “might have trouble meeting the [new] PFAS limits.”

Since PFAS levels are still a question mark, residents can better protect themselves with a home water filter that has an NSF rating of 53 or 58, for a filter or a reverse osmosis system respectively.

Does St. Louis Drinking Water Contain Fluoride?

Yes, St. Louis has been fluoridating its tap water since 1953. Previously, it aimed for a level of 1 part per million (ppm), but based on new public health guidelines, it reduced that target to 0.6 ppm in 2012. This amount of fluoride in water is considered safe to drink while still meeting the public health goal of reducing tooth decay.

Does St. Louis Drinking Water Contain Lead?

St. Louis relies on corrosion control measures to prevent the leaching of lead from pipes into drinking water. The Water Division reports that this approach has helped keep lead levels below the EPA’s action level of 15 parts per billion.

There are no lead mains in the St. Louis water system, but older homes with lead pipes or other plumbing materials could still have elevated levels of lead. If your home has a lead service line, it’s the homeowner's responsibility to replace it.

The St. Louis County Department of Public Health offers water testing for lead, copper, iron, and other metals at the DPH Environmental Laboratory. You can contact them at 314-615-8324 or environmentallab.dph@stlouisco.com.

Is St. Louis Water Quality Good Enough to Drink?

If you live in St. Louis, Missouri, or are just visiting, yes, you can drink the tap water. It has low levels of total dissolved solids (TDS) and is treated to remove pathogens that cause waterborne diseases. But the treatment process leaves behind chemicals like trihalomethanes, and other contaminants like chromium-6 may be present.

Installing a whole home filtration system like the UPSTREAM™ 4-Stage Whole Home Water Filter can reduce exposure to contaminants and give you peace of mind.

Take our filter quiz to find out which home water filter is right for you!