Portland, Maine’s tap water is consistently rated as highly safe, meeting or exceeding all federal and state standards for drinking water quality. The rigorous protection of the primary source and the advanced treatment processes ensure extensive monitoring. Residents can be confident in the quality of the water delivered to their community. This high level of safety results from the unique nature of the water source and robust infrastructure.
The Water Source and Management
The origin of Portland’s drinking water is Sebago Lake, Maine’s second-largest lake, which serves as a highly protected surface water supply. The lake benefits from a largely undeveloped and carefully managed watershed, contributing to exceptional raw water quality. The Portland Water District (PWD) is the utility responsible for the management, treatment, and delivery of this water. Due to its extraordinary cleanliness, Sebago Lake has historically earned an exemption from filtration requirements by the U.S. Environmental Protection Agency (EPA). This rare exemption is granted only to surface water supplies demonstrating superior source water protection.
Treatment Processes and Quality Assurance
Before distribution, the water undergoes a multi-step purification process at the Sebago Lake Water Treatment Facility. Treatment begins with screening and then uses a powerful dual disinfection method. The first step is ozonation, where ozone gas neutralizes harmful microorganisms like viruses and Giardia. Following this, the water is exposed to ultraviolet (UV) light to destroy chlorine-resistant protozoa, such as Cryptosporidium.
To prevent metal leaching from distribution pipes, the PWD implements corrosion control by adding sodium hydroxide. This raises the water’s pH to a target of 8.0, making the water significantly less corrosive. The final step involves adding chloramine, which maintains a disinfectant residual throughout the piping to the customer’s tap. The PWD’s state-certified laboratory conducts extensive quality assurance, performing more than 16,000 analyses annually, which surpasses minimum regulatory requirements.
Key Findings from Annual Water Quality Reports
Annual Consumer Confidence Reports (CCRs) consistently demonstrate that the distributed water is in full compliance with all Maximum Contaminant Levels (MCLs). The use of ozone as the primary disinfectant significantly reduces the formation of disinfection byproducts (DBPs). Routine sampling shows that DBP levels remain well below regulatory limits. Addressing emerging concerns, recent testing for Per- and Polyfluoroalkyl Substances (PFAS), including analysis of 29 different compounds, found no measurable amounts in the water supply. This proactively meets the new, stricter federal standards for PFOA and PFOS.
The systematic corrosion control program is designed to protect against the presence of lead and copper. While the water leaving the treatment plant is lead-free, the PWD’s 90th percentile result for lead is consistently below the EPA’s action level of 15 parts per billion. This reflects the success of their pH adjustment strategy.
Localized Factors Affecting Household Water Safety
While the water delivered by the PWD is of high quality, the final safety is influenced by the plumbing within an individual home. The primary concern is potential lead contamination from private service lines or internal plumbing installed before 1986. Even with corrosion control, stagnant water in older fixtures can absorb trace amounts of metal.
Homeowners can mitigate this localized risk by flushing the cold water faucet for thirty seconds to two minutes after the water has been sitting unused. Consumers should only use cold water for drinking and cooking, as hot water dissolves metals more readily. Residents concerned about lead exposure can request a certified test kit from the PWD.