Phoenix, Arizona
| Contaminant | Detected | EPA limit | EWG guideline | Status |
|---|---|---|---|---|
| Arsenic | 4.2 ppb | 10 ppb | 0.004 ppb | 1050× EWG |
| Chromium-6 (Hexavalent Chromium) | 0.52 ppb | — | 0.02 ppb | 26× EWG |
| Total Trihalomethanes (TTHMs) | 42.5 ppb | 80 ppb | 0.8 ppb | 53× EWG |
| Haloacetic Acids (HAA5) | 28.3 ppb | 60 ppb | 0.1 ppb | 283× EWG |
| Fluoride | 0.7 mg/L | 4 mg/L | 0.7 mg/L | 1× EWG |
| Uranium | 3.8 µg/L | 30 µg/L | 0.43 µg/L | 9× EWG |
| Total Hardness (as CaCO3) | 250 mg/L | — | — | — |
| Total Dissolved Solids (TDS) | 480 mg/L | — | — | — |
| Nitrate | 2.1 mg/L | 10 mg/L | 0.14 mg/L | 15× EWG |
| Lead | 1.8 ppb | 15 ppb | 0.5 ppb | 4× EWG |
Context
Phoenix has some of the hardest water in the United States, averaging 15-17 grains per gallon (250+ mg/L as CaCO3). This causes significant scale buildup in pipes, water heaters, and appliances, and many residents notice dry skin and hair. A water softener or conditioning system is one of the most common home water upgrades in the Phoenix metro area.
Arsenic occurs naturally in the groundwater throughout the Phoenix valley. While the city's surface water supply dilutes groundwater arsenic levels below the EPA MCL of 10 ppb, the detected level of 4.2 ppb still exceeds the EWG health guideline of 0.004 ppb by over 1,000 times.
Chromium-6 (hexavalent chromium) — the 'Erin Brockovich chemical' — is detected at 0.52 ppb, which is 26 times above the EWG health guideline. There is currently no federal MCL specifically for chromium-6; the EPA only regulates total chromium at 100 ppb. California has set a state-level MCL of 10 ppb.
As a desert city relying heavily on the Colorado River via the Central Arizona Project, Phoenix faces long-term water supply sustainability challenges. Drought conditions and Lake Mead water level fluctuations can affect source water quality and treatment requirements.
Common questions
Is Phoenix tap water safe to drink?
Phoenix tap water meets all current EPA legal standards and has no active violations. However, 6 of 10 detected contaminants exceed the stricter EWG health guidelines, including arsenic (1,050x above EWG), chromium-6 (26x above EWG), and disinfection byproducts. While legally compliant, many health-conscious residents choose to filter their drinking water with a reverse osmosis system.
Why is Phoenix water so hard?
Phoenix water averages 15-17 grains per gallon of hardness (250+ mg/L), classified as 'very hard.' This comes from the mineral-rich desert groundwater and Colorado River water that supply the city. The high calcium and magnesium content causes white scale on fixtures, reduced appliance lifespan, and soap scum buildup. A whole-house water softener is the most effective solution.
Does Phoenix water have arsenic?
Yes. Arsenic is naturally present in Arizona's groundwater and is detected in Phoenix tap water at 4.2 ppb. This is below the EPA maximum contaminant level of 10 ppb but exceeds the EWG health guideline of 0.004 ppb by over 1,000 times. Reverse osmosis systems are the most effective way to remove arsenic from drinking water at home.
What is the best water filter for Phoenix tap water?
For drinking water, a reverse osmosis (RO) system is the best choice for Phoenix. It removes arsenic, chromium-6, disinfection byproducts, fluoride, uranium, and reduces TDS and hardness. For whole-house protection against hard water scale, pair the RO with a water softener. See our recommended RO systems and water softener picks for Phoenix-specific options.
Does Phoenix add fluoride to the water?
Yes, Phoenix fluoridates its water at approximately 0.7 mg/L, which aligns with the CDC's recommended optimal level. This is well below the EPA maximum of 4.0 mg/L. If you prefer to remove fluoride, reverse osmosis, distillation, or activated alumina filters are effective options.
Is Phoenix water safe for babies and infant formula?
Phoenix water meets EPA safety standards, but the arsenic level (4.2 ppb) and fluoride content (0.7 mg/L) are concerns for infant health. The American Dental Association recommends using low-fluoride water for infant formula preparation. A reverse osmosis filter removes both arsenic and fluoride, making it the safest option for preparing baby formula with Phoenix tap water.
Phoenix's water quality story is defined by two factors: extreme hardness from mineral-rich desert sources, and naturally occurring arsenic and chromium-6 in the regional groundwater. The city's treatment infrastructure is modern and well-maintained, with no current EPA violations.
a blend of Salt River Project surface water (from the Salt and Verde Rivers via a system of reservoirs), Colorado River water delivered through the Central Arizona Project canal, and supplemental groundwater wells
This data reflects system-wide testing. Your home's plumbing may add or reduce contaminants.
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