Arizona’s municipal tap water is generally safe to drink because public water systems must meet strict federal standards set by the Environmental Protection Agency (EPA). These systems use extensive treatment processes to remove contaminants before the water reaches the tap. However, water safety is not uniform across the state. Quality depends significantly on the source, whether it is a regulated municipal supply or an unregulated private well. Understanding the specific challenges of the desert environment and local geology is important for determining water quality.
How Arizona Water is Sourced and Regulated
Arizona’s water supply comes from a mix of surface water and groundwater, with primary sources being the Colorado River, the Salt River Project (SRP) system, and extensive pumping from underground aquifers. Water providers utilize advanced infrastructure, such as the Central Arizona Project (CAP) canal, to move and treat large volumes of water for cities and agriculture. The complexity of these sources necessitates a robust regulatory framework.
The federal Safe Drinking Water Act gives the EPA authority to establish national drinking water standards, known as Maximum Contaminant Levels (MCLs). In Arizona, the Department of Environmental Quality (ADEQ) oversees and enforces these standards for all public water systems. ADEQ monitors water providers, ensuring they conduct required testing and maintain compliance. Water systems serving fewer than 15 connections or 25 people are typically considered private and are exempt from this regulation.
Naturally Occurring Contaminants in AZ Water
Arizona’s unique geology contributes to the presence of several naturally occurring elements in source water that require specialized treatment.
Arsenic
One significant concern is naturally occurring Arsenic, a semi-metal found in the state’s volcanic rock and soils, which can leach into groundwater. Arsenic is present in almost all Arizona groundwater supplies and must be reduced to the federal Maximum Contaminant Level of 10 parts per billion (ppb) before distribution. Long-term exposure to levels above the standard can increase the risk of skin, lung, and bladder cancers.
Fluoride
Fluoride is another naturally occurring element found in high concentrations in many Arizona aquifers due to fluoride-rich minerals. While fluoride is added to some public water systems to promote dental health, naturally occurring levels in certain areas can exceed the EPA’s MCL of 4.0 mg/L. Chronic consumption of water with elevated fluoride levels can lead to dental fluorosis (tooth mottling), and in severe cases, skeletal fluorosis, which affects bone and joint health.
Hard Water
High mineral content is a common characteristic of Arizona water, resulting in hard water. This hardness is caused by elevated concentrations of dissolved minerals, primarily calcium and magnesium. While these minerals do not pose a health risk, they can negatively impact water taste and cause scaling or buildup on plumbing fixtures and appliances.
Risks from Residential Plumbing and Private Wells
The quality of treated water leaving a municipal plant can change significantly as it travels through a home’s plumbing system.
For homes built before 1986, the primary risk comes from the potential for lead and copper to leach into the water from outdated service lines, fixtures, or lead-based solder. This is a localized problem unique to the property, not an issue with the public water source itself. Water utilities manage this risk by adding corrosion control agents during treatment to prevent metals from dissolving into the water supply.
Approximately 160,000 Arizona families rely on private wells. Unlike municipal systems, private wells are not regulated by the ADEQ or EPA, meaning the well owner is solely responsible for monitoring and ensuring the safety of their supply. Well water is particularly vulnerable to contamination from sources like septic systems and agricultural runoff, which can introduce high levels of nitrates and bacteria, such as E. coli. Because private well water quality can fluctuate seasonally, owners should regularly test their water for contaminants. Arsenic, nitrates, and bacteria are frequently found in excess of public health guidelines in unregulated wells.
Personal Filtration and Safety Measures
Consumers can take specific steps to confirm the safety of their water and improve its quality. The first step is to check the annual Consumer Confidence Report (CCR) provided by your public water supplier. This report details the results of required water quality testing and confirms compliance with federal standards.
To address common aesthetic issues like chlorine taste and odor, a simple activated carbon filter, such as a pitcher or faucet-mounted system, is highly effective. For consumers concerned about naturally occurring contaminants like arsenic and fluoride, or those relying on private wells, a reverse osmosis (RO) system is the most effective choice, as it can remove up to 99% of dissolved inorganic contaminants. If arsenic is a concern, boiling water should be avoided, as this process will concentrate the arsenic rather than remove it.
For homeowners with older plumbing, flushing the tap by running cold water for one to two minutes before drinking or cooking can help clear any metals that may have leached into the standing water overnight. Only use cold tap water for consumption, as hot water is more likely to dissolve and carry metals from the pipes.