Let’s consider a common question from Bay Area residents: where does our water come from? The immediate answer is that it pours from faucets and showerheads, but it’s less simple to track the path it takes to get there.

The main source of Berkeley’s water is located about 60 miles northeast, at the Mokelumne River watershed in the Sierra Foothills, which is filled by the Sierra's ice melt. The river’s bubbling waters once churned out gold nuggets, but now hydrate the banks of the Central Valley, feeding the wildflowers that grow sporadically across rocky shores.

As the water flows down to the Pardee Reservoir, it crosses the delta through the Mokelumne Aqueducts and then enters the East Bay Municipal Utility District (EBMUD).

“We’ve been blessed with a great water quality source,” said EBMUD’s Chief Information Officer Andrea Pook.

EBMUD’s Water Quality Manager Susan Teefy describes EBMUD as a small city: “We all do a lot of different things.”

These things include treating wastewater and returning water from pipes and sewers back to the bay. The facility also treats drinking water, purifying it until it reaches safe standards. These processes work together to ensure pristine quality from water coming both in and out of the bay.

“The water that we release to the bay is safe for the bay, but not for drinking. Drinking water quality has to be completely pathogen free, so the standard is very different,” said EBMUD’s Director of Wastewater Amit Mutsuddy.

Drinking water starts being monitored for quality by EBMUD at the top of the watershed. Samples are taken continuously downstream, including the terminal reservoirs that store water before it enters EBMUD for treatment. The water is tested again at the treatment plant, again as it leaves the plant through 4,000 miles of distribution pipes, and again at water storage tanks, water mains, and people's homes. If you’ve ever spotted a temporary sign with “EBMUD” printed on the front next to Berkeley’s sidewalks, this indicates that the area is currently being quality assured.

EBMUD’s water undergoes testing for both continuous and discrete variables. These continuous variables, including temperature, pH, and chlorine concentration, are consistently monitored. Other discrete variables, such as asbestos content, are monitored and treated more infrequently based on low current risk assessment data, which indicates the unlikelihood of finding specific toxins in the water.

“There’s a whole set of regulations,” said Teefy. “There's federal regulations, state regulations, and then even within the state regulations, our regulators can make additional requirements that apply just to us.”As concerns about synthetic, anthropogenic per- and polyfluoroalkyl substances (PFAS) or “forever chemical” contaminations grow, Teefy emphasized the safety of Berkeley’s water. Due to the remote location of the Sierra Foothills, the Mokelumne watershed remains relatively protected from PFAS, and park rangers from the East Bay Regional Park District patrol the area to keep the water safe.

“We are constantly looking for sources of contamination that might occur within the watershed, but up there we rely on these cooperative relationships,” Teefy said. “We monitor for about 29 chemicals, but we have not seen them yet.”

Though Berkeley’s drinking water has not yet been contaminated by PFAS chemicals, these forever chemicals are present within much of the Bay Area’s wastewater. As this wastewater is processed, organic matter called biosolids are recovered from the sewage. Biosolids are often used for fertilizer, commonly mixed with animal manure to improve soil fertility. However, these biosolids are becoming increasingly polluted by PFAS, which can contaminate crops.

“There are about 6,000 chemicals that we are watching with growing concern,” Mutsuddy said. “We don’t choose what comes into the plant. Everything that goes into the collection system we deal with, and not all of it we can remove.”

Misinformed reports have labeled water treatment agencies, like EBMUD, a source of PFAS chemicals. In reality, these chemicals originate from human products, including non-stick cookware, food packaging, textiles, cosmetic products, floss, shampoo, paints, turf, compostable utensils, and refrigerants, all which take copious amounts of energy to remove from water.

To help limit PFAS contaminants, individual consumers should avoid these products and opt for tested, PFAS-free alternatives. However, it falls on large corporations to limit the amount of synthetic chemicals in their products. Companies must be held accountable for the sustainability of their products and production systems, and one method of doing so is through limiting the presence of PFAS and other toxins.

Aside from synthetically generated PFAS chemicals, both wastewater and drinking water contain naturally occuring pathogens and other harmful substances. The purification process to treat for these contaminants is relatively simple. First, an aluminum-based coagulant is added to hydrolyze the water. The pathogens stick to it, and the water is poured into big concrete boxes of sand. This sand filters out the pathogens, and the water then flows into distribution pipes.

“It’s all gravity, all the way down,” Teefy said. “From a sustainability standpoint, you can't get much better than that.”However, the effects of the changing climate could complicate this filtration process. As raw water becomes more contaminated, for example from ash due to forest fires, it takes more energy to remove contaminants at the EBMUD facility. More coagulants and ozone must be pumped into the water supply, which increases energy consumption and raises customers’ water bills.

“Figuring out how to get done all that we need to do while still keeping the product affordable I think is our biggest challenge,” Teefy said. “We have to be sustainable.”

Once the water has been filtered and tested at EBMUD, it leaves the plant and travels through networks of pipes to reach peoples’ homes. At home, Teefy and Mutsuddy recommend consumers filter their water one last time.“If you suspect that where you're living has an old plumbing system, it wouldn’t be a bad idea to add a filter,” said Mutsuddy.

“We stock them in our warehouse. There's a time and a place for them,” said Teefy.EBMUD offers a testing program for water-consumers to send in additional samples to their facility. These samples are tested and returned to curious customers with a full quality report, including information about lead, PFAS, and other pollutants, many of which are caused by human activity.

Consistently facing new challenges to water treatment, EBMUD is focused on maximizing rate-payer dollars and minimizing energy expenditure. However, there are still customers that are unable to afford their water bills. Thus, EBMUD’s Customer Assistance Program (CAP) and Water Lifeline Program were created to assist low income residential customers. These programs ensure that all residents, regardless of income, have access to essential water services — a crucial step in combating resource-based inequity.

EBMUD’s emphasis on public outreach and building a strong relationship with customers is woven into the company’s practices and incentive programs. EBMUD and the Grammy Award-winning Alphabet Rockers dropped a music video in honor of World Water Day on March 22, 2025. The song, called “H2FLOW,” features incredible performances by Piedmont Avenue Elementary School students. The students helped brainstorm lyrics for the song, inspired by their love for water.

The journey that this water takes from the Mokelumne River to different locations across the Bay is carefully managed. EBMUD’s comprehensive testing, treatment, and monitoring maintains water quality amidst growing environmental complications, such as PFAS contamination and climate change. Despite these challenges, the company remains focused on sustainability and affordability while filtering safe water. Continued cooperation between consumers, regulators, and utility providers is crucial in safeguarding this vital resource for future generations. Next time you turn on your tap, take a second to imagine all the steps that are taken to keep your water clean and accessible.