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Treated Water Quality Summary

Need more details about your water?

Your water’s journey starts as mountain snowpack and ends with the clean, great-tasting water that comes out of your tap. Last year, we collected more than 35,000 samples and conducted more than 70,000 tests to ensure our water is as clean and safe as possible.

Some customers, such as beer brewers, pet stores or coffee shops, have more detailed questions about water hardness, metals and compounds than what’s included in Denver Water’s annual water quality reports. Those compounds, including emerging concerns, are listed below.

Watershed and reservoirs

Denver’s drinking water comes from rivers, lakes, streams, reservoirs and springs fed by high-quality mountain snow runoff. Denver Water’s supply is 100% surface water that originates in sources throughout 3,100 square miles of watersheds on both sides of the Continental Divide.

Treatment

Denver Water’s three treatment plants remove particulate matter and microscopic organisms that are found in surface waters. After filtration, chloramines are added as a disinfectant to inactivate potentially harmful microorganisms. Chloramines provide a longer lasting disinfection method than free chlorine, keeping water clean throughout Denver’s extensive distribution system. They also produce lower concentrations of disinfection byproducts than free chlorine.

Denver Water’s water quality laboratory analyzes and tests samples for compliant and noncompliant compounds. Some compounds may not be regulated by state or federal agencies, but Denver Water monitors them. All drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that the water poses a health risk.

Water quality monitoring

Denver Water serves 25% of the state’s population with less than 2% of all water used in the state. The natural environment is our lifeline, and we help protect it by promoting wise water use. We take our water quality very seriously. Last year we collected more than 35,000 samples and conducted more than 70,000 tests to ensure our water is as clean and safe as possible. Denver Water vigilantly safeguards our mountain water supplies, and the water is carefully treated before it reaches your tap. As you’ll see below, Denver Water rarely, if ever, exceeds safe levels of contaminants.

Your water is safe to drink, bathe and clean.

Compounds we monitor that are not listed in our annual water quality report include:

Compound or Organism Name

Category

Summary

Regulated?

2020 Average

2020 Range

Maximum Contaminant Level

Total coliforms and
E. coli

Microbiological

Opportunistic bacteria that can be harmful if ingested. Escherichia coli (E. coli) is a specific species of coliform essential to the human digestive tract and causes serious illness when encountered outside of that context. Sampled throughout finished water distribution system to verify system containment.

Yes

0.04%
(Excludes invalid test results)

0% – 0.5%

5%

Heterotrophic Plate Count (HPC)

Microbiological

Measures the variety of bacteria commonly found in water. This is often helpful information that is used to gauge how well-maintained the water system is.

Yes

1.4 CFU (colony forming units)

Nondetect – 88

N/A

pH

Inorganic

Characteristic that describes the acidity or neutrality of a water-based solution.

No

8.7 SU (standard units)

7.6 – 9.6

N/A

Hardness

Inorganic

Amount of minerals dissolved in water, namely calcium and magnesium.

No

100.0 ppm (parts per million)

50 – 151

N/A

Alkalinity

Inorganic

Property of water that describes its ability to neutralize added acids and bases while maintaining its pH.

Yes

64.0 ppm

37 – 108

N/A

Inorganic Anions

Bromide

Inorganic

Found within Earth’s crust and sea water. Interaction with disinfectant chemicals may produce disinfectant byproducts.

No

0.05 ppm

Below reporting limit – 0.2

N/A

Chloride

Added during drinking water treatment for disinfection.

No

21.5 ppm

4.6 – 37.8

N/A

Fluoride

Naturally occurring in water from interaction with soils and bedrock. Can be added to public drinking water to reduce dental cavities.

Yes

0.6 ppm

Below reporting limit – 1.2

4

Nitrate

Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits.

Yes

0.1 ppm

Below reporting limit – 0.2

10

Nitrite

No

0.03 ppm

Below reporting limit – 0.2

1

Orthophosphate

Sources include agricultural and residential fertilizers. A nutrient essential to the growth of plants, but too much present in water leads to overgrowth of oxygen-consuming bacteria that concentrate minerals and organic matter in the water source. For this reason, it is monitored in environmental water sources as an indication of water quality.

No

Below reporting limit

Below reporting limit

N/A

Sulfate

Can become present in surface water through contact with naturally occurring sulfate minerals.

No

45.9 ppm

13 – 66

N/A

Metals

Aluminum

Inorganic

Abundant in Earth’s crust. Aluminum salts used in municipal water treatment to purify water.

No

35.7 ppb (parts per billion)

13.3 – 230.6

50 ppb

Antimony

Naturally occurring in ore deposits and widely used in the production of flame retardants. It is a known human carcinogen.

Yes

Below reporting limit

Below reporting limit

6 ppb

Arsenic

Natural component of the Earth’s crust; if found in water, the source is usually groundwater. Known to be toxic to humans and manifests as skin lesions and cancer.

Yes

Below reporting limit

Below reporting limit

10 ppb

Barium

Mainly used as a drilling fluid additive for oil/gas operations. Exposure to high levels is linked to adverse effects on blood pressure and kidney function.

Yes

32.4 ppb

14.6 – 47.8

2,000 ppb

Beryllium

Naturally occurring in ore deposits and is used in metal alloy production. Long-term exposure has the potential to damage human bones and lungs.

Yes

Below reporting limit

Below reporting limit

4 ppb

Cadmium

Used primarily for metal coating/plating for a variety of industries. Long-term exposure may result in liver, kidney, bone and blood damage.

Yes

Below reporting limit

Below reporting limit

5 ppb

Calcium

Essential nutrient for human bone and teeth development. Contributor to water’s hardness. Presence in water from interaction with exposed rocks.

No

27.7 ppm

17.2 – 29

N/A

Chromium

Trivalent configuration is naturally occurring in Earth’s crust and is an essential nutrient for humans. Hexavalent configuration is produced by metal production operations and is a known carcinogen.

Yes

1.0 ppb

Below reporting limit – 2.1

100 ppb

Copper

Naturally occurring metal found in rocks, soil and sediment. Elevated level likely the result of plumbing and fixtures interacting with corrosive water.

Yes

3.9 ppb

Below reporting limit – 36.1

1,300 ppb

Lead

Chronic exposure detrimental to child neurological development. Lead detected in drinking water likely the result of plumbing and fixtures interacting with corrosive water.

Yes

Below reporting limit

Below reporting limit

15 ppb

Magnesium

Contributor to water’s hardness. Presence in water from interaction with exposed rocks. Principal cause of scale formation in boilers, water heaters and pipes.

No

7.1 ppm

1.5 – 13.2

N/A

Mercury

Extremely poisonous substance with multiple routes of absorption. Released into the environment through natural weathering processes.

Yes

0.06 ppb

0.05 – 0.1

2 ppb

Molybdenum

Considered an essential trace element for humans and animals. Found widely throughout nature, normally in trace amounts, though mining operations contribute to large discharges.

No

6.2 ppb

Below reporting limit – 20.8

N/A

Selenium

Common element in Earth’s crust and an essential dietary element. At high concentrations, some selenium compounds may cause damage to the nervous system.

Yes

Below reporting limit

Below reporting limit

50 ppb

Sodium

Widely distributed in environment. Added in during water treatment process in chemicals that assist with pH adjustment.

No

20.6 ppm

6.3 – 37.4

N/A

Thallium

Used most often in electronic research equipment. Exposure to high levels can cause nerve damage, and long-term exposure may result in changes to blood chemistry.

Yes

Below reporting limit

Below reporting limit

2 ppb

Uranium

Naturally occurring radionuclide in granite and other mineral deposits. Long-term exposure increases the risk of cancer and kidney damage.

Yes

Below reporting limit

Below reporting limit

30 ppb

Total Organic Carbon (TOC)

Organic

Naturally occurring, carbon-containing compounds in water indicative of the presence of living organisms (twigs, bacteria, etc.)

Yes

1.8 ppm

0.9 – 50

Treatment technique

Dissolved Organic Carbon (DOC)

Organic

The fraction of water’s total organic carbon content that can pass through a 0.22 micron filter.

Yes

1.6 ppm

1.2 – 2

Treatment technique

Disinfectant By-Products (DBPs)

HAA5

Organic

Formation of trihalomethanes (TTHMs) and/or haloacetic acids (HAA5) occurs when chlorine-based disinfectants used during the treatment process react with organic matter in water. The lab monitors organic compounds in the water with molecular configurations that form THMs when disinfectant is added. The data generated via UV-254 is used in the calculation of Specific Ultraviolet Absorption (SUVA), a secondary requirement for water treatment.

Yes

12.8 ppb

5.9 – 26.2

60 ppb

TTHM

Yes

25.0 ppb

9.3 – 42

80 ppb

Taste & Odor (T&O) Compounds

Geosmin

Organic

Molecules released from algae occurring in freshwater sources that are not lethal/toxic when ingested but are not aesthetically pleasing when present in water. The lab monitors two of the most prevalent compounds; geosmin and 2-methylisoborneol (MIB).

No

2.8 ppt (parts per trillion)

Below reporting limit – 10

N/A

2-methylisoborneol
(MIB)

No

2.5 ppt

Below reporting limit – 5

N/A

Volatile Organic Compounds (VOC)

1,1,2-Trichloroethane

Organic

Compounds that contain carbon and are a gas at room temperature but can be found in several different forms throughout the environment. Most VOCs of interest are used as solvents in the production of other chemicals or are useful in the production of plastic-type products. The analytes listed here were selected because they are either known or suspected carcinogens.

Yes

Below reporting limit

Below reporting limit

5 ppb

1,2-Dichloroethane

Yes

Below reporting limit

Below reporting limit

5 ppb

1,2-Dichloropropane

Yes

Below reporting limit

Below reporting limit

5 ppb

1,2,3-Trichloropropane

No

Below reporting limit

Below reporting limit

N/A

1,4-Dioxane

No

Below reporting limit

Below reporting limit

N/A

Benzene

Yes

Below reporting limit

Below reporting limit

5 ppb

Carbon tetrachloride

Yes

Below reporting limit

Below reporting limit

5 ppb

Dichloromethane

Yes

Below reporting limit

Below reporting limit

5 ppb

Styrene

Yes

Below reporting limit

Below reporting limit

100 ppb

Tetrachloroethylene

Yes

Below reporting limit

Below reporting limit

5 ppb

Trichloroethylene

Yes

Below reporting limit

Below reporting limit

5 ppb

Vinyl Chloride

Yes

Below reporting limit

Below reporting limit

2 ppb

Ammonia (NH3)

Inorganic

Often added during the disinfection of drinking water with chlorine to create chloramines; this reduces the formation of DBPs during disinfection and prolongs the period in which treated water can be deemed disinfected post-treatment.

No

85 ppb

136 – 1,680

N/A

All data in table reflect samples taken from the distribution system, treatment plant effluents, or both.

Emerging contaminants

  • Perfluorocarbons (PFCs) — Poly-fluorinated-carbons (PFCs) and poly and per-fluoroalkyl substances (PFAS) are found in food packaging, cookware, outdoor gear, furniture, carpeting and aqueous film forming foams (AFFF) used in firefighting. Results from continuous monitoring for both source and treated water showed no detectable levels of PFCS in Denver’s water.
  • Cyanotoxins — Cyanobacteria, commonly known as blue-green algae, are a class of aquatic microorganisms that can produce cyanotoxins. Health effects include gastrointestinal discomfort, liver inflammation, and skin rashes or dermatitis. Climate change is causing these algae blooms to occur more often than they used to. Denver Water continuously monitors and samples its source water for the presence of cyanobacteria and nutrient concentrations that favor bloom occurrences. Denver Water can switch or augment its source water to optimize water quality. To date, Denver Water has not had any detectable levels of cyanobacteria in its source or distribution water.
  • Microplastics Plastic materials are found everywhere and are slow to degrade. Microplastics are characterized as plastic material smaller than 5 millimeters and larger than 10 nanometers, but most concerning are plastic particles smaller than 25µm (micrometers) because they can pass into human tissue, causing inflammation and digestive problems. Denver Water is working with other labs and water industry professionals to develop consistent, repeatable and widely available methods of detecting and quantifying plastics in drinking water.
  • Taste and odor During the height of runoff throughout summer and the rapid temperature changes of the fall, there may be instances in which water will have an unusual or unfamiliar taste and/or odor when dissolved organic compounds are released from the dynamic microscopic community of organisms (including diatoms, plankton, zooplankton, algae and cyanobacteria) that are present in source water. These compounds are not harmful for human consumption; however, Denver Water continuously monitors and adjusts its source water to minimize potential taste and odor events. Denver Water can add powder activated carbon (PAC) into the treatment process to remove these compounds to make drinking water more palatable.
  • Lead — The water that Denver Water provides to homes and businesses is lead-free, but lead can get into the water as it moves through lead-containing household fixtures, plumbing and water service lines — the pipe that brings water into the home from the main in the street — that are owned by the customer. Denver Water is underway with its Lead Reduction Program, a 15-year effort to locate and replace the estimated 64,000 to 84,000 lead service lines in our service area.
  • Pharmaceuticals – These compounds enter water systems through trace amounts passing through consumers as well as disposal of medications into sinks or toilets. Denver Water monitors for these compounds in its source water, particularly areas that may be influenced by treated wastewater and agriculture. To date, Denver Water has not had any detectable levels of pharmaceuticals in its source or distribution water.

Help us keep your drinking water clean

Denver Water’s Cross-Connection Control and Backflow Prevention Program protects the public water supply from pollutants and contaminants that could, under certain circumstances, be drawn into the public water supply from private properties. All commercial, industrial, domestic, irrigation and fire line services are required to have an approved backflow prevention assembly installed.

A backflow prevention assembly installed on the service line allows water to only flow into the building, preventing water from flowing in the opposite direction into the drinking water system. The sole purpose of a backflow prevention assembly is to prevent your drinking water from becoming contaminated.

What causes a backflow event?

Backflow is the unwanted flow of water or other liquids, mixtures, gasses or substances into the drinking water supply.

There are two main ways backflow can occur:

  • Backsiphonage occurs when there is a negative pressure in the water distribution system, which draws the water from a private water system into the public water system. This can occur at any time, such as during a water main break or during a large firefighting effort.
  • Backpressure occurs when the pressure in a private water system exceeds the pressure in the public water distribution lines that can cause normal flow to reverse. A pump used to increase the water pressure within a building’s plumbing system to reach a higher floor might cause this.

Click image to see it larger.

Without Backflow Prevention Assembly

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Without Backflow Prevention Assembly

Why is a survey/test/installation necessary now, but was not required before?

In 2016, the state passed State Regulation 11.39, mandating water utilities provide and maintain a cross-connection control and backflow prevention program. Water purveyors are required by the Colorado Department of Public Health and Environment to survey all water services to determine if potential hazards to the potable water supply are protected by a backflow prevention assembly.

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In 2016, there was 66% completion rate, in 2017 88% completion rate, in 2018 a 93% completion rate, in 2019 a 95 percent completion rate, in 2020 a 96% completion rate (the goal was 91%), in 2021 a 96% completion rate (the goal was more than 95%).

What happens when Denver Water inspects my water service line?

A Denver Water employee will locate the water service line connection to the building. Then the employee will document the property type and any potential hazards, such as pesticides, chemicals, nonpotable water and others, to the water distribution system.

Backflow prevention assemblies contain the hazard from the potable water distribution system and are required to be tested annually. Denver Water processes more than 40,000 cross-connection control backflow test reports annually and reports the tests to the Colorado Department of Public Health and Environment to ensure the safety of your drinking water.

Backflow testing compliance

The charts below show the number of assemblies in Denver’s service area that comply with state regulations, as well as the number of surveys Denver Water completed between 2016 and 2020. Denver Water has completed more than 60,000 surveys of backflow assemblies to comply with state regulations.

Denver Water tested 37,970 backflow assemblies. That’s a 95% completion rate, well above the Colorado Department of Public Health and Environment’s requirement of 80%.

Denver Water has completed 62,606 service connection surveys for a 98% completion rate. The Colorado Department of Public Health and Environment requires more than 95%.