The cleanliness of America’s water supplies is a true masterpiece of public health. In fact, water treatment was highlighted by the Centers for Disease Control as one of the top achievements of the 20th Century.

We treat your drinking water to ensure high-quality taste, purity and clarity. However, on rare occasions, you might notice a different taste, odor or discoloration in your water, or you may even be asked to boil your drinking water before consuming or using it.

The following page outlines some of the most common questions regarding drinking water quality and we work together to ensure that your water is safe and aesthetically pleasing.

For more information on how we ensure that you are drinking safe water, please read our most recent Water Quality Report Card.


Discoloration of your drinking water may be caused by anything ranging from air bubbles in the water system to sediment or corroded piping. Read on to learn more about causes and possible solutions.

Milky or cloudy water is often caused by air bubbles in the water system. Cloudiness and air bubbles do not present a health risk. Typically, air enters the distribution system because of changes in the water temperature or during construction and repairs.

If you notice cloudy water, fill a glass with tap water and let it sit for a few minutes. The cloudiness and air bubbles should naturally disappear.

Flushing your cold water tap for 5-10 minutes should clear up the cloudy water. If the cloudy water does not disappear after 10 minutes of flushing, please contact our Water Treatment Plant Laboratory staff at 919-537-4228 or

Water heaters are a common source of yellow or brownish water. If the discoloration is only seen in your hot water, accumulated sediments in the bottom of the hot water tank are the likeliest source. We recommend flushing water heaters annually, following the manufacturer’s instructions or contacting a licensed plumber for advice.

If your cold water is also affected, the cause might be iron or manganese sediments that have settled in the water pipes over time. Iron and manganese are both naturally present in our reservoirs. In addition, iron pipes in our distribution system can be a source of iron discoloration. Maintenance and repair work, nearby construction or flushing of water pipes (such as from a hydrant or other release point) may stir up these particles and cause discoloration. Iron and manganese in drinking water are not a health risk.

Discoloration is usually temporary and should disappear after water is flushed from the distribution system or your home plumbing. However, we recommend not drinking tap water if it is discolored. In addition, do not wash clothes when water appears rusty, because the rust can stain fabric. Flushing your cold water tap for 5-10 minutes should clear up discolored water. 

If your water is green or greenish-blue in color, this may indicate deterioration of copper plumbing (e.g., in a water fountain). We recommend consulting with a plumber to find the source of deterioration and a possible solution.

Black particles are often just accumulated iron and manganese in water. As previously stated, iron and manganese are both naturally present in our reservoirs. In addition, iron pipes in our distribution system can be a source of these particles. Maintenance and repair work, nearby construction, or flushing of water pipes (such as from a hydrant or other release point) may stir up these particles. Iron and manganese in drinking water are not a health risk.

Another common cause of black particles in tap water is the disintegration of rubber materials used in plumbing systems. Sources of the rubber materials are typically:

  • toilet flappers
  • rubber washers and o-rings
  • membranes in thermal expansion tanks on water heaters
  • liners disintegrating from the inside of flexible hoses underneath sinks or on water heaters

Rubber materials need to be replaced periodically. We recommend replacing the deteriorating rubber with one that is resistant to chloramines.

White particle buildup comes from a variety of sources and most commonly originates from the hot water system. Typically, this buildup is either calcium carbonate or from a type of brass corrosion called dezincification. Dezincification is the selective release of zinc from brass, and it can affect brass with high zinc content. Direct connections of different types of metals, water velocity, water chemistry and higher temperatures can facilitate dezincification of susceptible brass.

Also, dissolved calcium is naturally found in our drinking water and can change to calcium carbonate in hot water heaters. Over time, calcium carbonate may accumulate at the bottom of your water heater and collect in your faucet aerators. OWASA recommends periodically flushing your water heater to remove any sediment buildup.

Bacteria, mold and fungi can grow on surfaces where water is exposed to air (e.g., in a toilet bowl, around sinks or showers). They may appear black or pink in color. These growths are produced by airborne fungal spores or bacteria and are not originated from drinking water. We recommend periodically scrubbing and cleaning the toilet, shower, or sink with cleaning products containing bleach.

Taste & Odor

From spring through fall, an earthy or musty taste or smell may result from compounds produced by algae growing in our Cane Creek Reservoir or University Lake. Algae and other aquatic plants are common in lakes, and these plants normally grow most in the warm to hot months of the year. Growth of algae is related to factors such as a warmer than normal winter, rainfall, sunlight, and levels of phosphorus and nitrogen compounds in lake water.

Although our drinking water treatment process removes algae, some taste and odor-causing compounds may remain. The compounds are harmless, but are noticeable to some people at very small levels. Some people can notice odorous compounds from algae at levels as low as 5 parts per trillion; one part per trillion is like one drop of water diluted into 20 Olympic-size swimming pools.

Also, during the fall, as the surface of the lakes cools to the same temperature as the bottom waters, mixing of the water layers occurs. This stirs up sediment that can contain compounds with unpleasant taste and odor.

We do anticipate these impurities, and we try our best to combat them. For example, we add a chemical called permanganate to water as it is pumped from our lakes. This substance neutralizes taste- and odor-causing compounds. Also, as the lake water enters our water treatment plant, we add powdered activated carbon during the first phase of treatment for additional removal of taste- and odor-causing compounds.

The length of time it takes for musty taste and odor to improve can vary throughout our service area. This is due to mixing of the fresher, better-tasting water with water that has a noticeable taste and odor within our 390 miles of drinking water pipes and water tanks.

You may need to flush your internal plumbing once the water in the OWASA pipe serving the area has less noticeable taste and odor. Some customers minimize hot-water use during taste and odor events. If this is the case, noticeable odor may linger in hot water due to the continued mixing of the old water in the hot-water tank with fresher, better-smelling water. Flushing the water heater according to the manufacturer’s instructions will help resolve this issue once fresher water with less noticeable taste and odor is available.

In the meantime, you can add lemon slices to water to neutralize the odor or taste, or filter your water with a pitcher featuring an activated-carbon filter.

We use chlorine as a primary disinfectant, and a mixture of chlorine and ammonia called “chloramines” as a secondary disinfect, throughout the year to neutralize bacteria and other waterborne pathogens. We regularly test the levels of chlorine and chloramines in our water, and we follow Federal and State standards for the minimum and maximum levels of these disinfectants in the water system. However, every March, we use chlorine as both our primary and secondary disinfectant in the treatment process. We make this disinfection change one month per year to provide a more intense level of disinfection, as recommended by the US Environmental Protection Agency and NC Department of Environmental Quality. Thus, in early spring, we often receive calls about a chlorinated taste or smell in drinking water.

If the taste and odor of chlorine becomes overly unpleasant, we have a few recommendations:

  • Filter water with an activated carbon filter.
  • Add a few lemon slices to a pitcher of water. Ascorbic acid in lemon neutralizes chlorine.
  • Let water sit in a refrigerator for about a day so chlorine will have time to dissipate from the water.
  • Boil water for one minute to evaporate the chlorine.

What is a Boil Water Advisory?

A Boil Water Advisory is a public health recommendation from OWASA advising customers to boil their tap water before using it. This is in response to an event that could have allowed contaminants to enter the distribution system. Because the water quality is unknown, customers should assume the water is unsafe to drink and take appropriate precautions.

OWASA issues Boil Water Advisories as a precautionary measure. The Boil Water Advisory is a recommendation, and it is issued when contamination is possible, but unconfirmed. It is different from a Boil Water Notice, the next level of alert. A Boil Water Notice is issued when contamination is confirmed, and boiling water is therefore required.

Below are some answers to your frequently asked questions.

Boil Water Advisory Frequently Asked Questions

When does OWASA issue a Boil Water Advisory?

Typically, we issue a Boil Water Advisory after a water pipe break or repair, small or widespread loss of pressure in our water system or a natural disaster. In some cases, our crews can repair a water pipe while maintaining adequate pressure to prevent contamination from entering the water distribution system, and when we perform a repair in this way, no Boil Water Advisory is needed.

When we issue a Boil Water Advisory, we notify only the customers affected. If the risk of contamination is widespread, OWASA will arrange publicity in the news media, publish information on our website and more to inform the public.

How long will a Boil Water Advisory be in effect?

An advisory will remain in effect until bacteriological test samples show the water is safe to drink. Testing typically takes 24 to 28 hours to complete.

What should I do during a Boil Water Advisory?

Boil tap water before using it for drinking, making ice, washing dishes, brushing teeth, or preparing food. Bring tap water to a rolling boil for at least one minute and let it cool.

Should I use my coffee maker, water or ice dispenser when a boil water advisory is in effect?

During an advisory, do not use water from any appliance connected to your water lines, including water and ice dispensers in your refrigerator or freezer. Use boiled or bottled water to make coffee and ice.

How should I wash dishes during a Boil Water Advisory?

Household dishwashers are generally safe to use if the water reaches a final rinse temperature of at least 150 degrees Fahrenheit or if the dishwasher has a sanitizing cycle.

To wash dishes by hand:

  • Use boiled water, or
  • Wash and rinse dishes as normal. Then, in a separate basin, add one teaspoon of unscented household bleach for each gallon of warm water. Soak dishes in the basin for at least one minute. Let dishes air-dry completely.

Should I bathe or shower during a Boil Water Advisory?

It is safe to bath or shower, but be careful not to swallow any water. Use caution when bathing babies and young children. Consider giving them a sponge bath to reduce the chance of them swallowing water.

Can I wash my hands during a boil water advisory?

Yes. Vigorous hand-washing with soap and your tap water is safe for basic personal hygiene. However, if you are washing your hands to prepare food, you should wash your hands with boiled (then cooled) water or bottled water and hand-washing soap. Alternatively, you could wash hands with tap water, followed by the use of hand sanitizer.

What if I drank some of the water before I found out about the advisory?

This advisory was issued as a precaution, so your risk of getting sick is very low. However, if you begin to have a fever, diarrhea or nausea, seek immediate medical attention.

How will I know when the advisory or notice has been lifted?

We will rescind the Boil Water Advisory when the results from the testing have been confirmed that the water is safe to drink. You will receive your notification the same way you were informed of the advisory, whether that be by email or text, door hanger or a news alert in local media. You can also contact the Water Treatment Laboratory staff at 919-537-4228 or

Substances of Special Interest

We do our best to deliver high-quality drinking water to you. This includes, of course, testing for all regulated compounds, neutralizing bacteria and pathogens, removing sedimentary particles, filtering out contaminants and disinfecting the water before it reaches you. However, there are certain substances in which you may be interested regarding its possible presence in your drinking water.


OWASA adds fluoride to drinking water to help prevent tooth decay, as recommended by the Centers for Disease Control. In accordance with national guidelines, the fluoride level in our water is 0.7 of one part per million (ppm). This level of fluoride is much lower than the Federal regulated maximum of 4 ppm and the levels occurring naturally in raw water, which range up to 14 ppm in groundwater. We closely monitor scientific research, guidelines, regulations and best practices regarding fluoridation.

Fluoride Frequently Asked Questions

What is fluoride?

Fluoride is a solid form of the noble gas, fluorine. Naturally occurring fluoride minerals are found underground, in groundwater and, in some places, in river and lake waters, though not in detectable levels in OWASA reservoirs.

How much fluoride is in an eight-ounce glass of OWASA drinking water?

An eight-ounce glass (237 mL) of OWASA water contains 0.17 mg of fluoride.

When did fluoridation begin in our community?

The public water system in Chapel Hill and Carrboro has provided fluoridated drinking water to help protect dental health since 1964, when the University owned the water system. OWASA continued fluoridation when it began serving the community in 1977.

What fluoride compound does OWASA use?

We use hydrofluorosilicic acid.

What is the quality of the fluoride OWASA uses?

All fluoride used by OWASA meets the purity standards of the National Sanitation Foundation and the American Water Works Association for use in drinking water treatment. In November 2012, we had our fluoride tested by an independent laboratory for arsenic, cadmium, chromium, lead, mercury and other metals; no metals were detected at the laboratory’s reportable levels.

Where does OWASA get the fluoride it adds to drinking water?

OWASA buys fluoride from the Unimin Corp. in Bakersville, NC. The company’s fluoride is a co-product from its mining and production of quartz materials.

What is OWASA’s annual cost for fluoridation?

We spend about $25,000 annually to buy fluoride for use at our water treatment plant. $25,000 equals a fraction of 1% of our annual budget of about $40 million.

Is there fluoride in OWASA lake water?

No. The concentration of natural fluoride in our source water is so low that we cannot detect any.

In accordance with Federal requirements, our annual Water Quality Report Cards include a statement that potential sources of fluoride in drinking water include erosion of natural deposits or discharge from fertilizer and aluminum factories. However, there are no fertilizer or aluminum factories in the watersheds of our Cane Creek Reservoir and University Lake.

Is it safe to use fluoridated water in making baby formula?

According to the American Dental Association, it is safe to use fluoridated water to mix infant formula. The only risk is that of an increased chance of mild tooth discoloration, known as enamel fluorosis.

What can I do if I want to remove fluoride from OWASA water?

Two methods are effective for removing fluoride: reverse osmosis and distillation. Citizens can also purchase commercially treated water which has been filtered to remove fluoride. If you’d like to read more about water fluoridation, including a list of bottled waters without fluoride, we invite you to follow these links:

OWASA One-Page Summary on Water Fluoridation
Waters without Fluoride and Local Suppliers
Information from State, Federal, National, & International Organizations Regarding Fluoridation

Lead & Copper

In cities with older water systems, lead may be present in public water mains because lead was used many years ago as a pipe material, due to its easy pliability, ability to withstand corrosion, and near-universal availability. Some water systems used lead goosenecks, a small section of pipe, to connect the water main to the service line. OWASA’s water system has no known lead pipes, and OWASA looked for and removed lead goosenecks from our water system in the 1990s.

Copper, on the other hand, is still used as a pipe material. Along with its durability, copper exhibits antimicrobial tendencies. The Environmental Protection Agency regulates lead and copper at the federal level due to their impacts on human health.

We test for lead and copper in our treated drinking water when it leaves the Jones Ferry Road Water Treatment Plant and in samples collected from homes throughout our service area. OWASA has always been in full compliance with the EPA’s Lead & Copper Rule.

Lead & Copper Frequently Asked Questions

How does lead get into drinking water?

Lead is not typically found in sources of drinking water supplies such as lakes. Lead can enter drinking water from corrosion of plumbing materials that contain lead.

  • Lead pipes and service lines: The OWASA water system has no known lead pipes. We also removed all known lead goosenecks from our water system in the 1990s.
  • Lead solder: Solder is used to connect pipes in household plumbing. In 1986, lead solder was banned from use in household plumbing. Copper plumbing installed prior to 1986 may contain lead solder.
  • Fittings and fixtures: Home plumbing fittings and fixtures can contain lead. Effective January 2014, the Reduction of Lead in Drinking Water Act lowered the allowable lead content of fittings and fixtures sold in the US from 8% to 0.25%.

What does OWASA do to minimize corrosion and the release of lead?

In the 1990s, OWASA removed all known lead pipes, including “goosenecks,” from our water system. We also have an effective corrosion control program, which includes monitoring and managing the drinking water chemistry and adding a phosphate compound. The phosphate forms a protective coating inside pipes and fixtures to control corrosion in our public water system and in private plumbing. To ensure optimized corrosion control, we monitor corrosion control parameters in treated drinking water as it leaves the water treatment plant and within our water system.

What does OWASA do to check for lead in drinking water?

Federal and State testing requirements require public water systems such as OWASA to test for lead in drinking water collected from customers’ homes as part of the Lead & Copper Rule. Samples must be collected from homes that meet criteria set by the EPA; these criteria identify “high-priority” homes that are most likely to have elevated lead levels. The number of homes and frequency of testing is determined by population size and compliance history.

Because of our compliance with monitoring requirements, we have been granted approval for reduced monitoring status. Every three years, we test for lead in drinking water in 30 homes built from 1983 to 1985 that we have identified as possessing copper pipes with lead solder. In the past five rounds of monitoring, we have had only one sample with a measurable level of lead, and the result was below the regulatory limit. We have never discarded or invalidated a sample result.

We also provide lead & copper testing of our drinking water at no charge when requested by a customer. Analysis is performed by an independent contract laboratory. Test results are reported in our annual Water Quality Report Cards. To request a lead & copper test kit, please contact our laboratory staff at 919-537-4228 or

How are lead and copper samples collected?

Detailed instructions are provided in each sample kit. Lead and copper samples are collected by residents from taps or faucets that are used regularly.

There are several important factors with this testing: there must be a period of at least six hours during which the tap at which the sample will be taken and any adjacent or nearby taps are not used; no pre-flushing should be performed; the aerator should not be removed prior to sampling; and wide-mouth bottles are used for collecting lead and copper samples.

What can you do to reduce lead exposure?

If you have old water pipes or suspect that your plumbing system may release lead into our drinking water, we recommend the following:

  • Please contact us about having your drinking water tested for lead.
  • Do not use hot water for drinking and cooking. Hot water is more likely to contain lead.
  • Do not use hot water to make formula for infants, cereal or a beverage.
  • Boiling water does not remove lead.
  • If you haven’t used a faucet for six or more hours, flush the stagnant water out of your plumbing pipes by running the water for three to five minutes, or until it is cold as it will get.
    • CONSERVATION TIP: This water can be used to water decorative plants.
  • As part of your regular household maintenance, remove and clean faucet aerators. Over time, lead particles and sediment can collect in the aerator screen located at the tip of your faucet.
  • Drain your water heater annually. Over time, metals, sediment and bacteria can build up in your water heater.

The EPA provides additional measures to reduce lead in home drinking water.

How can I check what the pipes in my system are made of?

While OWASA has removed all known lead pipes in our system in the 1990s, and our staff has not found any lead service lines over many years of work, you may wish to check the composition of your service line.

Lead pipes are dull gray and very soft. They are easily identified by carefully scratching the surface with a key or other dull metal object; do not use a knife or other sharp object. If the pipe is lead, the scratched surface will be shiny, like a new nickel. Note that there’s a difference between lead and galvanized pipes. Galvanized pipes are also dull gray, but the surface remains dull when scratched. Also, strong magnets will stick to galvanized pipe. Copper pipes will look like a new penny when scratched. Plastic pipes are also used for service lines in our area. They are commonly black or white.

Note: Service lines are the pipes that connect your home or business to our water mains, and the portion between the meter and the home or business is owned by the property owner.

Chromium 6

Chromium is a metal found in rocks, soils, plants, water and animals. The most common forms of chromium in the environment are trivalent (chromium 3), hexavalent (chromium 6), and the metal form. Chromium 6 is one of the forms of chromium and the most-oxidized form. The US Environmental Protection Agency (EPA) is currently reviewing results from a long-term animal study, which suggests that chromium 6 may be a human carcinogen if ingested, and other recent research.

How does chromium get into water?

The major source of chromium 6 in drinking water is natural chromium present in some types of rock. There are also industrial sources of chromium, but our local watersheds are highly protected and, as far as we know, do not currently contain any of these sources.

However, in anticipation of potential new Federal regulations, OWASA performed a study in 2011 to determine the sources of chromium 6 in our drinking water. We identified one of our treatment chemicals as the main source. We discontinued use of this product and reduced the levels of chromium 6 in our water by over 75%.

What are the limits on total chromium and chromium 6 in drinking water?

The EPA limits total chromium in drinking water to a maximum of 100 parts per billion (ppb). This level was set assuming all chromium detected is in the form of chromium 6. Currently, there are no federal limits for individual forms of chromium in drinking water, but states are allowed to set regulations that are stricter than federal regulations.

Does OWASA test for chromium 6?

In testing from November 2013 to August 2014, we detected chromium 6 at levels ranging from less than 0.03 ppb to 0.06 ppb. Testing results from multiple utilities are available below; results vary because utilities have different water sources and treatment processes.

Does water treatment remove or reduce chromium 6?

Conventional water treatment has demonstrated the ability to remove chromium 3 from water, but does not remove chromium 6. Advanced technologies such as ion exchange, reverse osmosis and microfiltration were successful in reducing chromium 6 concentration to less than 1 ppb in bench-scale and pilot-scale testing.

We continue to closely monitor scientific research and the EPA’s action on chromium 6, as well as other currently unregulated substances in drinking water, and will take action when necessary for your safety and the safety of our water.


A group of compounds of emerging concern are per- and polyfluoroalkyl substances, known collectively as PFAS.

PFAS are used in a variety of everyday products to increase resistance to water, grease, or stains such as carpet, clothing, fabric for furniture, paper packaging for food, cookware and other materials. Thus, they are commonly found in household dust, as well as household discharges to wastewater. They are also used industrial processes and in in aqueous firefighting foams (AFFF) used at airfields and other high temperature fires.

Detectable concentrations of PFAS can enter lakes, rivers or groundwater through industrial releases, discharges from wastewater treatment plants and the use of AFFF. Often, due to their specialized uses, PFAS in water are localized and associated with a specific facility, such as fire-training facilities, military bases, domestic airports and manufacturing sites. Treated effluent from wastewater treatment plants and biosolids land-application sites are conveyors of PFAS that enter the wastewater stream from household products and other concentrated sources.

While research is still being conducted to confirm the health effects of PFAS, these chemicals have been linked to a higher risk of cancer, liver disease, developmental disorders and immunodeficiency. In 2016, largely in response to these concerns, the EPA established a lifetime Health Advisory Level of 70 parts per trillion (ppt) for the combined amount of two PFAS — perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) — in drinking water. PFOA and PFOS are the two PFAS most-extensively produced and studied.

PFAS research is emerging. It is also complex. We look to the federal and state government to turn this research into science-based laws that protect our community. And we are committed to sharing available information about PFAS with you in an accessible manner — in terms of where and how information is distributed, and with language that is not overly technical. We have developed a background document with information on the timeline of PFAS detection in North Carolina, State & Federal actions and steps OWASA takes to monitor for such substances locally.

We monitor for PFAS once per quarter and include our results in our quarterly reports to local governments. We have also sent information directly to customers, for example, in our 2018 Water Quality Report Card, mailed to all OWASA account holders.


OWASA’S PFAS Monitoring Program

OWASA tests your water for PFAS compounds every quarter. In 2018, we proactively tested both the Cane Creek Reservoir and University Lake for PFAS. We detected two PFAS compounds in University Lake water and 11 PFAS compounds in Cane Creek Reservoir water. As a result of those results, we now quarterly test the raw water from Cane Creek Reservoir, as well as drinking water as it is leaving the Water Treatment Plant.

The results show that our treatment process is removing PFAS from the raw water. Drinking water leaving the water treatment plant consistently measures well below the health advisory limit of 70 parts per trillion for PFOA and PFOS.

We are not required by law to meet an EPA health advisory, but we strive to meet all health advisories as added protection to our community. The health advisory level for PFAS helps us assess treatment options and evaluate if additional treatment or operational changes are needed.

PFAS Monitoring Program Results

The definite sources of PFOS and PFOA in the Cane Creek Reservoir are unknown. There are no facilities typically associated with elevated levels of PFAS in the watershed, although we do not have specifics on past land use. 

The sum of PFOS and PFOA in these samples is consistently well below the health advisory level of 70 parts per trillion (ppt). Studies indicate that the use of powder activated carbon (PAC), as used in OWASA treatment process, lowers PFAS levels in drinking water; our test results showed that OWASA we successfully removed some PFAS, but not all.

We are not required by law to meet an EPA health advisory, but we strive to meet all health advisories as added protection to our community. The health advisory level for PFAS helps us assess treatment options and evaluate if additional treatment or operational changes are needed.

We have also begun to test the effluent leaving the Mason Farm Wastewater Treatment Plant. In a recent samples, we have detected 11 to 12 PFAS compounds leaving the wastewater treatment plant. All sampling events were consistently below 70 ppt for PFOS and PFOA combined.

We are also testing water in Morgan Creek upstream of our discharge.

PFAS Monitoring Program Results

Testing for Unregulated Compounds

The US Environmental Protection Agency (EPA) periodically requires water utilities to test drinking water for various compounds which could become subject to new Federal standards. The EPA uses data collected by the utilities and scientific research when deciding whether to adopt new standards.

These testing requirements, called the Unregulated Contaminant Monitoring Rule (UCMR), are part of the Safe Drinking Water Act. To date, there have been four rounds of UCMR testing, each focusing on a separate set of compounds. OWASA has participated in all four rounds and will continue to participate in future iterations of the UCMR.

The tables linked below show the data OWASA collected in each round of UCMR testing. Results are also reported in our Annual Water Quality Report Card in years data are collected.


We will continue to closely monitor scientific research, the EPA’s action on regulated and unregulated compounds, and available treatment technologies, taking appropriate actions when necessary to ensure the safety and reliability of our water.