The majority of Tempe’s potable water is produced at two conventional surface water treatment plants, the Johnny G. Martinez Treatment Plant and the South Tempe Water Treatment Plant. Tempe also utilizes groundwater wells to produce potable water and supplement surface water supplies.

Each plant receives surface water originating from the Salt River Project (SRP) and Central Arizona Project (CAP). SRP surface water delivered to Tempe is collected from the Salt and Verde River watersheds, stored in six SRP reservoirs and diverted into SRP canals at Granite Reef Dam in Mesa, Arizona. SRP also supplements surface water supplies by pumping groundwater wells located along the canal systems into the water conveyance. Tempe also receives a portion of Colorado River water, which is delivered through the CAP canal system to central Arizona including the Phoenix and Tucson metropolitan areas.

Fluctuations in water characteristics are dependent on the blends of source water being supplied to Tempe’s treatment plants . The mix changes seasonally and year to year, depending on precipitation and annual runoff from snowmelt in the mountains. The Salt River is characteristically higher in total dissolved solids (TDS) and chlorides (Cl^-), while the Verde River is higher in hardness compounds (expressed in CaCO₃).

Recent water quality results and ranges can be found on the City of Tempe’s Annual Water Quality Report, also known as the Consumer Confidence Report (CCR).

Learn more about Tempe’s water sources by reviewing the Water Resources Master Plan.  

Fluoride occurs naturally in Arizona’s surface and groundwater sources at around 0.2 to 0.4 parts per million (ppm) or mg/L. The City of Tempe complies with Federal drinking water standards in order to maintain adequate fluoride levels in drinking water for dental health. This is done by adding additional fluoride to a concentration of 0.7 ppm. At this level, fluoride strengthens the enamel of teeth and helps to prevent tooth decay, erosion and cavities.

Supplementing the fluoride produces water considerably below the current EPA-established maximum contaminant level (MCL) of 4.0 mg/L. For additional information on fluoridation, contact the American Dental Association or seek advice from a dentist.

There are several reasons tap water may be temporarily cloudy or cloudy when frozen.

It may be caused by microscopic air bubbles in the water. This is a natural phenomenon, caused by dissolved air in the water that is released when the faucet is opened. If air is the cause, the water usually clears within a few minutes if allowed to stand. Since the water system is pressurized, this phenomenon usually occurs at the tap, resulting in cloudy water and/or ice cubes.

Other times, dissolved minerals like calcium and magnesium form a solid when frozen making ice cubes cloudy. There may be minerals floating in the glass when cloudy ice cubes melt. These minerals are safe to consume.  

Scale formed from dissolved minerals, like calcium and magnesium, are on surfaces like teapots, coffeepots, shower heads and doors, or anywhere else that water has evaporated. These dissolved minerals are not harmful to human health.

Taste and odor are aesthetic qualities of drinking water that are not regulated by state or federal drinking water quality standards, but Tempe strives to provide drinking water that is aesthetically pleasing to its customers. Common inquiries regarding drinking water taste and odor are addressed in the following bullet points:

• Chlorine: Chlorine is a common disinfectant that is added to the city’s drinking water. Chlorine is added in order to maintain a chlorine residual within the water distribution system  required to eliminate or kill harmful bacteria and microorganisms. Chlorine levels up to 4 ppm are considered safe for human consumption by the U.S. Environmental Protection Agency. Tempe maintains a chlorine residual closer to 1 mg/L.
• Earthy or Musty: Seasonal occurrences of musty/moldy or earthy tastes and odors may be detected in the system water. Research, by laboratories dedicated to this subject, has determined the culprits are naturally occurring algal and fungal by-products. As algae in the canals die, compounds known as Methyl-Isoborneol (MIB) and Geosmin are released into the water. These stable complex compounds present in just parts per trillion (ppt) are difficult to remove with current technology. The detection of these compounds is dependent upon an individual's olfactory sensitivity. Many people may never detect them, while others who are sensitive may detect the musty/moldy taste and smell at levels below instrument detection levels. Tempe uses activated carbon to adsorb the MIB and Geosmin, thus alleviating the taste and odor. Tempe in conjunction with Salt River Project (SRP), Central Arizona Project and other valley cities, have participated in various studies to determine where the algae is most concentrated and the best way to control and alleviate the musty/moldy occurrence. Additionally, Tempe and SRP manage the canals and lakes to reduce the algal growth. Research has determined that there are no indications of adverse health effects attributed to the water from these compounds.
• Rotten eggs: Rotten egg-like odors can be caused by Hydrogen Sulfide gas and/or other sewer gases emanating from dried out P-shaped traps in drains common in plumbing fixtures like sinks, showers or bathtubs. Organic material present in P-traps from rotting, mildewing dirt and hair debris within the fixture can also impart an offending odor. These foul odors are often mistaken as coming from tap water. One tip to accurately determine if these odors are coming from the tap water is to fill a clean glass with cool water from the fixture at the source of the odor, walk away from the drain or sink and let the water settle for a few minutes before checking the odor.

Offensive odors coming from fixture drains may be reduced or eliminated by flushing fixtures with plenty of water. Flushing ensures that P-traps will not dry out allowing sewage vapors to escape into the home. Flushing fixtures also helps to keep the drain fresh by removing excess decaying matter from within the drain that may be causing unpleasant odors.

Tempe's water meets all the federal, state and local water quality standards. Therefore the use of secondary water treatment devices is not needed. Furthermore these devices may cause more water quality problems if not properly maintained. However, some people choose to install treatment systems for aesthetic reasons such as hardness deposits or chlorine taste, which are secondary standards and not regulated by the State of Arizona. The EPA has also developed a brochure that contains more information about tap water: Water on Tap: what you need to know. The brochure has information about types of treatment devices and their functions and limitations. For more information on choosing the unit that will fit the unique needs of the household, refer to the following sources:

• National Sanitation Foundation (NSF) is a global public health organization that independently tests and certifies home water treatment products to ensure that devices meet standards for safety, quality, and performance. Review NSF’s recommendations for choosing a drinking water filter.

Although not required by federal, state or local regulations, Tempe has conducted monitoring of source waters and drinking water for pharmaceuticals and other personal care products (PPCP). Specifically, Tempe’s Water Utilities Division (WUD) worked with the American Water Works Association Research Foundation and the National Science Foundation’s Water Quality Center at Arizona State University to research the occurrence of personal care products and pharmaceutical compounds in our drinking water supplies and how these compounds can affect our customers. To date, research throughout the world has not demonstrated an impact on human health from pharmaceuticals and endocrine disrupting compounds in drinking water.

Tempe strongly encourages residents to properly dispose of unused or expired prescription drugs by bringing them to Tempe’s Household Products Collection Center, a preferred alternative to flushing them down the toilet. The Household Products Collection Center is located at 1320 E University Drive. The Arizona Department of Environmental Quality has additional recommendations for disposal.

The compound Hexavalent Chromium, Chromium 6 or Cr-VI has gained much attention. These are generally produced by industrial processes such as electroplating, stainless steel production, leather tanning, textile manufacturing and wood preservation. Exposure occurs through inhalation, ingesting contaminated food or water or by direct contact with skin. Acute exposure may cause eye, nasal or skin irritation. Chronic exposure may lead to eye, kidney or liver damage and can cause lung, nasal or sinus cancer.

Although there is no current federal, state or local regulation specifically for Hexavalent Chromium, Tempe has been conducting quarterly monitoring of all drinking water sources since 2008.

In January 2011, the Environmental Protection Agency released an optional monitoring protocol to assist public water systems in gathering occurrence information for Hexavalent Chromium. Following the EPA’s protocol, Tempe conducted monitoring in February 2011 using more sensitive methodology to analyze detection levels down to 0.05 ppb at all of its drinking water sources and in its distribution system. The results ranged from non-detect (<0.05 ppb) to 7.2 ppb. Tempe continues to proactively monitor Hexavalent Chromium, remaining vigilant of emerging public health information regarding this chemical contaminant.

Currently, the EPA has a maximum contaminant level (MCL) for Total Chromium of 100 parts per billion (ppb), which includes all forms of Chromium. There is not a separate MCL for Hexavalent Chromium. Tempe has never exceeded the federal, state or local standard for the MCL for Total Chromium.

"Hard" water refers to drinking water that contains more dissolved minerals than "soft" water. Hard water is common in most of the United States, especially in the southwest and Arizona. Common hardness minerals, like calcium and magnesium, are naturally present in the rock formations surrounding Arizona’s aquifers, causing these minerals to be dissolved in groundwater water. Magnesium and calcium are positively charged ions knowns as cations. When cations are present in high concentrations (as they are with hard water), this can require individuals to need more soap and detergents to get the same cleaning affect.

The Environmental Protection Agency (EPA) has established standards for drinking water that fall into two categories: Primary Standards and Secondary Standards. Primary Standards are based on health considerations, and Secondary Standards are based on aesthetics such as taste, odor, color and corrosivity. There is no Primary or Secondary standard for water hardness. Water softeners are used to help eliminate or reduce hardness but are limited in what they can do.

Customers often inquire about the hardness of their drinking water, which is expressed in grains per gallon, in order to properly adjust the settings on dishwashers or water softeners. To calculate grains per gallon, divide the hardness value in mg/L by 17.1.  Customers interested in learning more about water hardness values are encouraged to check out the City of Tempe’s most recent Water Quality Report.

If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with private service lines and home plumbing. When tap water comes into contact for an extended amount of time with lead pipes, copper pipes with lead solder or other leaded materials, lead or copper from the piping may leach out into the drinking water. The City of Tempe is responsible for providing high quality drinking water but cannot control the variety of materials used in home plumbing components. When water has been sitting for several hours, minimize the potential for lead exposure by flushing the tap for 30 seconds to two minutes before using water for drinking or cooking. For more information on lead in drinking water, testing methods and steps residents can take to minimize exposure, visit the Environmental Protection Agency (EPA) website: epa.gov/SafeWater/lead.

The EPA published the Lead and Copper Rule Revisions (LCRR) in the Federal Register on January 15, 2021. The LCRR became effective on December 16, 2021, and public water systems, including the City of Tempe, will be required to comply with the rule by October 16, 2024. The LCRR includes multiple new requirements for water systems, focused on the following six key areas further reducing potential exposure to lead in drinking water and improving public education regarding lead:

• Identifying areas most impacted
• Strengthening treatment requirements
• Systematically replacing lead service lines
• Increasing sample reliability
• Improving risk communication
• Protecting children in schools and childcare facilities

In preparation for the LCRR, Tempe is working with water quality experts and regulatory agencies to develop and implement a LCRR compliance strategy and ensure compliance with the rule revisions by October 2024.

Tempe residents concerned about lead or copper can take the following precautions to minimize leaching from the home plumbing:

• Flush the cold water tap after periods of non-use. Flush the cold-tap water for one to two minutes when using for cooking and drinking after the water has not been used for more than six hours (for example, overnight or during the workday). Flushing will ensure that the water is representative of the water from the distribution mains and not from the residential plumbing. Flushing is important because the longer water is exposed to the lead pipes or lead solder, the greater the possibility of lead contamination. The flushed water can be collected and used for cleaning, on houseplants and gardens.
• Use cold water for consumption: Use only water from the cold tap that has been thoroughly flushed for consumption. Never cook with or consume water from the hot water tap because hot water dissolves lead more quickly than cold water.

The City of Tempe established a ban on the use of lead solder and lead pipes for construction in May of 1988. If planning to re-plumb a house or have any plumbing repaired, it is the homeowner’s responsibility to ensure the use of low-lead materials, as required by the 1991 Lead and Copper Rule.

Other environmental sources of lead are:

• Leaded paint
• Leaded gasoline
• Lead contaminated dust/soil
• Ceramic pitchers or plates with lead-based glazes
• Leaded crystal
• Lead soldered seams of certain canned foods (acidic foods are especially susceptible to lead contamination)
• Brass and chrome plated faucet fixtures
• Some imported spices or toys

For more information about lead, visit the Environmental Protection Agency’s website or contact Tempe’s Environmental Services at 480-350-4311.

For a list of certified laboratories for water testing, visit the Arizona Department of Health Services website.