Tempe Water Quality: How Does It Compare to the Rest of AZ?

Where Does Tempe’s Tap Water Come From? 

Tempe’s tap water comes from multiple sources around the state of Arizona. First, it relies on surface water from the Salt River and Verde River watersheds. This water flows through Salt River Project (SRP) canals into six SRP reservoirs. 

 The city gets additional water from the Colorado River, which flows through canals maintained by the Central Arizona Project (CAP), a 336-mile system. 

 A third source of water is groundwater, which is pumped up through wells at various points throughout the system. 

How Is Tempe’s Drinking Water Treated? 

Tempe’s tap water is treated at one of two locations: the Johnny G. Martinez Treatment Plant and the South Tempe Water Treatment Plant. It goes through a multi-stage water treatment process that includes: 

• Coagulation, or the addition of chemicals that cause particles to stick together 
• Flocculation, a mixing process that produces even larger clumps of particles 
• Sedimentation, in which these clumps settle to the bottom of the basin 
• Filtration, or the passage of water through sand or anthracite filters 
• Disinfection, which in this case includes the addition of sodium hypochlorite and ultraviolet (UV) light treatment 

The City of Tempe also maintains a wastewater treatment system so that water can be “reused for energy generation, irrigation of non-food crops and riparian habitats.” 

Why Does Tempe’s Drinking Water Smell or Taste Bad? 

Variations in Tempe’s drinking water are more likely to be a matter of preference than a health issue. Tempe’s water quality is monitored with at least 120 monthly water tests for E. coli, coliforms, and other bacteria that can cause waterborne diseases. 

According to Tempe’s water FAQs, if your water tastes earthy or musty, it’s most likely caused by “algal and fungal by-products” and isn’t a public health risk. A rotten egg smell could be caused by organic matter or gasses in your drains or P-traps. 

Of course, you can always have your tap water tested or call a licensed plumber to ensure your water heater and other devices are working correctly. 

Which Contaminants Are Found in Tempe Tap Water? 

The Safe Drinking Water Act (SDWA) requires public water systems in the USA to keep contaminant levels below levels set by the Environmental Protection Agency (EPA.gov). Although Tempe's water quality meets most EPA guidelines, other organizations, like the Environmental Working Group (EWG), recommend more cautious limits. 

Here are five of the most concerning contaminants in Tempe tap water: 

Arsenic 

Arsenic is a heavy metal with significant health effects, including arsenic poisoning and even death, when consumed over time or in large doses. Arsenic is more common in regions that rely on groundwater systems, including aquifers and private wells. 

Tempe’s tap water is relatively high in arsenic: below the EPA’s legal limit of 10 parts per billion (ppb), but 820 times higher than the EWG’s recommendation: 

• EPA maximum allowance: 10 ppb 
• EWG recommended maximum: 0.004 ppb 
• Tempe maximum contaminant level: 3.28 ppb 

Chromium-6 (hexavalent) 

Chromium-6 is a known carcinogen that made headlines in the 1990s thanks to Erin Brockovich’s advocacy in Hinckley, California. Although the EPA regulates chromium levels overall, there’s no legal limit for this type of chromium. 

The EWG recommends a maximum of 0.02 ppb to protect public health. Tempe’s tap water exceeds this level by 116 times: 

• EPA maximum allowance: No legal limit 
• EWG recommended maximum: 0.02 ppb 
• Tempe maximum contaminant level: 2.33 ppb 

Haloacetic acids (HAA9) 

Haloacetic acids are a group of nine disinfection byproducts that are formed during the water treatment process. Although disinfectants help keep your water safe to drink, these byproducts are associated with an increased cancer risk in high doses. 

The EWG recommends an upper limit of 0.06 ppb for HAA9 — which Tempe’s drinking water quality exceeds by 491 times: 

• EPA maximum allowance: No legal limit 
• EWG recommended maximum: 0.06 ppb 
• Tempe maximum contaminant level: 29.4 ppb 

Perfluorooctanoic acid (PFOA) 

Perfluorooctanoic acid (PFOA) and other forms of PFAS have only recently caught the attention of regulators. The EPA has set a proposed limit of 4 parts per trillion (ppt) for PFOA due to its association with cancer and other health effects. 

Tempe’s tap water is currently over this proposed limit, and exceeds the EWG’s more cautious recommendation by 887 times: 

• EPA maximum allowance: 4 ppt (proposed limit) 
• EWG recommended maximum: 0.007 ppt 
• Tempe maximum contaminant level: 6.21 ppt 

Total trihalomethanes (TTHMs) 

Trihalomethanes form another category of disinfection byproducts measured as total trihalomethanes (TTHMs). These include chloroform and bromoform, and they may lead to an increased risk of certain cancers, including skin and bladder cancer. 

Tempe’s trihalomethane levels are 321 times higher than the EWG’s recommendation: 

• EPA maximum allowance: 80 ppb 
• EWG recommended maximum: 0.15 ppb 
• Tempe maximum contaminant level: 48.2 ppb 

Is Tempe’s Tap Water Hard or Soft? 

Drinking water is described as hard or soft based on its mineral content. Since Tempe’s water sources contain naturally occurring minerals like calcium and magnesium, it has relatively hard tap water compared to other cities in the U.S. 

 Hard water is safe to drink. However, it can have an unpleasant taste and leave residue on skin, cookware, and other surfaces. Residents of Tempe may want to install a home water softener to remove excess minerals from their tap water. 

Can Water Filters Improve Tempe Water Quality? 

Yes, home water filters can improve the taste and quality of your drinking water, but the right water filter for you will depend on which contaminants you want to remove: 

• Activated carbon filters: Effective at removing disinfection byproducts and improving the taste and smell of your tap water. 
• Reverse osmosis filters: Effective at removing heavy metals like lead and arsenic and forever chemicals like PFOA. 
• Water softeners: Effective at removing unwanted minerals like calcium and magnesium, but don’t filter out other contaminants or kill bacteria. 

Consider a multi-stage filtration system that incorporates multiple water treatment methods, like the UPSTREAM™ 4-Stage Whole Home Water Filter X, for best results. 

Does Tempe’s Tap Water Contain Lead? 

According to the City of Tempe’s FAQs, any lead in Tempe’s drinking water comes from lead pipes and plumbing, not from the city’s water sources. The City is in the process of replacing lead service lines, but private service lines and plumbing materials, especially in homes built or plumbed before 1988, could be a source of lead exposure. 

If you’re concerned about lead in your drinking water, the Arizona Department of Health Service has provided a list of certified drinking water laboratories to get it tested. 

In the meantime, flush your tap water before using it, only use cold water for cooking and drinking, and install a home water filter that’s certified to remove lead. 

Does Tempe’s Tap Water Contain Fluoride? 

Yes, Tempe’s tap water contains fluoride, which is used as a public health measure to prevent dental problems. Arizona’s water resources contain naturally occurring fluoride of around 0.2 to 0.4 parts per million (ppm). Tempe adds additional fluoride to reach recommended levels of 0.7 ppm while staying below the EPA’s regulatory maximum of 4 ppm. 

Can You Swim in Tempe Town Lake? 

No, you can’t swim in Tempe Town Lake. This 2-mile-long lake was formed by damming the Salt River riverbed and filling it with water. Because it’s considered an artificial body of water, it would have to follow the same regulations as a swimming pool, with lifeguards and water quality testing required to allow swimming. 

Swimming is only allowed for triathlons and other permitted events, and unsanctioned swimmers can be fined up to $1,000. 

Is Tempe’s Tap Water Safe to Drink? 

Tempe’s tap water is considered safe to drink according to the Safe Drinking Water Act. However, it contains high levels of arsenic, PFOA, disinfection byproducts, and other contaminants that may pose health risks over time. Tempe’s water quality can vary throughout the year and is considered “hard” due to its mineral content. 

Tempe residents can install a home water filter to remove unwanted contaminants and improve the taste of their tap water. Take our quiz to find out which type of filter is right for you, and get 20% off your first purchase!