Is Portland, OR Tap Water Safe to Drink?

Where Does Portland Get Its Water?

Portland, OR draws its drinking water from multiple sources, including surface water from the Bull Run River system and groundwater from the Columbia South Shore well field. The primary utility serving most of the city is the Portland Water Bureau, which manages both the Bull Run watershed and the blended well supply.

The Bull Run River Treatment Plant is the main surface water facility, treating water from the protected Bull Run watershed east of the city. Groundwater from the Cascade wells is blended with Bull Run water at a separate entry point and treated before distribution.

Several neighboring utilities also serve parts of the greater Portland area. These include Clackamas River Water, the City of Milwaukie, Rockwood PUD, Sunrise Water Authority, and Tualatin Valley Water District, each drawing from the Clackamas River or groundwater sources to serve communities on the city's edges.

How Is Portland Tap Water Treated?

Portland's water goes through several treatment steps before reaching your tap. These include coagulation, slow sand filtration, granular activated carbon filtration, membrane filtration, and additional processes for groundwater including aeration and disinfection. The combination is designed to remove sediment, organic material, and chemical contaminants.

Disinfection uses free chlorine as the primary method, with other disinfectant approaches applied at specific points in the system. This kills bacteria and viruses and maintains a residual level of disinfectant through the pipes to your home. Some disinfection byproducts can form as a result, which is a normal trade-off in treated drinking water.

Groundwater sources go through additional treatment steps, including UV treatment and separate well-specific treatment trains, before being blended with Bull Run surface water. The Joint Water Commission provides an additional entry point for some service areas, reflecting the region's interconnected water supply network.

What's in Portland Tap Water?

The most notable finding is lithium, detected at up to 58.2 micrograms per liter (µg/L) in recent EPA samples. EPA's health reference level for lithium is 10 µg/L, and one ZIP code in the Portland area had readings above that benchmark. It is important to note that there is currently no federally enforceable legal limit for lithium in drinking water; the 10 µg/L figure is a non-regulatory screening level.

PFAS compounds were also detected across Portland's water system. PFTrDA, a type of long-chain PFAS, was found at 0.007 µg/L in one ZIP code, matching EPA's current guideline for that specific compound. Several other PFAS substances, including HFPO-DA, PFBA, and 11Cl-PF3OUdS, were detected at or at the reporting threshold but did not exceed applicable guidelines.

Lithium in drinking water typically enters from natural geological sources in soil and rock, not industrial pollution. PFAS compounds can originate from a wide range of industrial and consumer product sources and persist in the environment, which is why EPA has recently increased its focus on monitoring them nationwide.

Health Risk Profile for Portland

The lithium reading of 58.2 µg/L is more than five times EPA's non-regulatory health reference level of 10 µg/L. Because there is no enforceable federal maximum for lithium in tap water, this is not a legal violation, but it is a signal worth paying attention to, particularly for certain groups. EPA's health reference level is set as a precautionary benchmark based on available health data.

Infants, pregnant individuals, and people with kidney conditions are generally considered more sensitive to lithium exposure. At very high levels, lithium can affect thyroid and kidney function. The detected levels here are far below therapeutic doses used in medicine, but ongoing exposure through drinking water is a reasonable concern for the most vulnerable household members.

For PFAS, a filter certified to NSF/ANSI 58 (reverse osmosis) or NSF/ANSI P473 (which specifically targets PFOA and PFOS class PFAS) is the most effective choice. NSF/ANSI is an independent third-party certification program, and filters carrying that label on the box have been tested to perform as claimed. For lithium reduction, reverse osmosis filters certified to NSF/ANSI 58 can also be effective, making that type a practical all-around option for Portland households with concerns.

The PFAS levels detected in most of Portland's system were at or near the detection threshold, meaning the actual concentration in your tap water may be very low. Science on long-term low-level PFAS exposure is still developing, and EPA continues to update its guidance. Filtering at the tap is a reasonable precaution, especially for infants and pregnant individuals.