The Unfiltered Truth About San Francisco Water Quality

Where Does San Francisco Water Come From?

San Francisco sources its water from the San Francisco Regional Water System (SFRWS), which is owned and operated by the San Francisco Public Utilities Commission (SFPUC). The most well-known reservoir supplying the city is the Hetch Hetchy Reservoir, located about 160 miles away in Yosemite National Park. Fed by the Tuolumne River and collecting meltwater from the Sierra Nevada mountains, the Hetch Hetchy Reservoir serves not only San Francisco but also multiple other Bay Area communities, benefitting around 2.7 million people in total.

The SFRWS also includes other reservoirs located in the Sierra Nevada, Alameda County, and San Mateo County. Groundwater is stored in a deep aquifer in northern San Mateo County and the western side of San Francisco. The diverse mix of water sources provides resilience against natural disasters, regulatory changes, and climate uncertainty, and helps in supplying over 7 million people in and around the city.

How Is San Francisco Water Treated?

The SFPUC is responsible for treating and testing around 200 million gallons of water daily before it reaches consumers. Although Hetch Hetchy water is of such high quality that it's exempt from state and federal filtration requirements, it still gets tested over 90,000 times per year. Instead of filtration, the water undergoes treatment that includes disinfection with ultraviolet light and chlorine, pH adjustments for corrosion control, and fluoridation for dental health.

Water from reservoirs in Alameda County is treated at the Sunol Valley Water Treatment Plant, while water from San Mateo County reservoirs is treated at the Harry Tracy Water Treatment Plant. These plants employ filtration, disinfection, fluoridation, and other processes to ensure water quality. The city mainly relies on Hetch Hetchy and local reservoirs, supplementing with a small amount of groundwater blended in the transmission pipelines and Sunset Reservoir.

Is San Francisco Water Clean?

San Francisco’s stance on environmental sustainability didn’t come by chance. It developed due to necessity. The city has a history of environmental problems that still haunt them today. In fact, in 2021, the West Sunset Well which supplies the city with drinking water, was shut down indefinitely after they discovered the presence of carbon tetrachloride. “Carbon tet” is a cancer-causing industrial solvent that’s main use as a dry cleaning agent was phased out in 1960.

Despite the city's focus on sustainability, San Francisco water quality challenges persist. The San Francisco Bay, for instance, exceeds state water quality standards for various contaminants like pesticides, metals, and other toxic substances.

While this doesn't directly impact the city's drinking water, which primarily comes from Hetch Hetchy, it raises concerns about the overall environmental health of the region. Aging sewage infrastructure and occasional sewage spills have also led to impaired water quality, affecting both aquatic ecosystems and beachgoers.

Furthermore, the Bay Delta Watershed, which plays a critical role in supplying other parts of California with water, faces its own challenges. These include declines in fish populations and increasing vulnerability to climate change impacts like sea level rise and flooding. In the context of climate change, water management is becoming increasingly precarious. Potential impacts to the surrounding regions include more extreme weather, shifting precipitation patterns, constant drought, and low water flows.

Is It Safe to Drink the Tap Water in San Francisco?

According to the San Francisco Water Quality Report and the U.S. Environmental Protection Agency (EPA), San Francisco's tap water is safe to drink. However, it's important to understand that compliance with regulatory standards doesn't necessarily mean that the water is free of all contaminants.

Since the Safe Drinking Water Act was enacted in 1974, the EPA has established enforceable guidelines that public water systems must adhere to, covering 92 specific contaminants commonly found in water supplies across the United States.

These regulations are important but not exhaustive. Thousands of other potential contaminants, such as microplastics, which are increasingly present in global water supplies, aren't yet regulated, mainly because we can’t reliably test for it.

Similarly, PFAS, which have been associated with bladder cancer and nervous system issues for decades, are only now beginning to face possible regulation. Although companies started voluntarily phasing out PFAS over two decades ago, the EPA has just proposed enforceable limits in 2023.

According to the Environmental Working Group (EWG), a Washington D.C.-based water watchdog, the proposed changes in regulations mark the first shift in water quality standards in over two decades even though our understanding of various contaminants and their potential risks has advanced significantly during that time.

Unfortunately, regulation often lags behind current scientific understanding. As pointed out by the EWG, many of the existing U.S. and San Francisco water quality standards are outdated and not reflective of current scientific consensus.

Let’s look deeper at specific substances present in San Francisco's water that may raise concerns despite being within legal limits.

Which Chemicals Are Hurting San Francisco Water Quality?

San Francisco water quality has some unique challenges. Much of it doesn’t need to be filtered, the heavy use of chlorine and chloramines with unfiltered water can cause other problems. Disinfection byproducts form when chemical disinfectants interact with organic matter. As you’ll see, they are a big problem in San Francisco. But not their only problems.

Haloacetic Acids (HAA5)

HAA5 is made up of five haloacetic acids: monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid. These chemicals are known as disinfection byproducts, as they result from disinfectants like chlorine interacting with organic matter in water. Long-term exposure to HAA5 can lead to cancer.

Levels of HAA5 in San Francisco water have exceeded what the EWG recommends for safety by 319 times:

• EPA maximum allowance: 60 parts per billion (ppb)
• EWG recommended maximum: 0.1 ppb
• San Francisco maximum contaminant level: 31.9 ppb

Haloacetic Acids (HAA9)

HAA9 includes all of the contaminants from HAA5 but adds bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, and tribromoacetic acid. These are also disinfection byproducts and are also cancer-causing.

Levels of HAA9 in San Francisco water have exceeded what the EWG recommends for safety by 658 times:

• EPA maximum allowance: No legal limit
• EWG recommended maximum: 0.06 ppb
• San Francisco maximum contaminant level: 39.5 ppb

Total Trihalomethanes (TTHMs)

TTHMs — like the haloacetic acids above — are formed when chlorine interacts with organic compounds in drinking water. They’re also known to be carcinogenic. This category is made up of four chemicals: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.

Levels of TTHMs in San Francisco water have exceeded what the EWG recommends for safety by 274 times:

• EPA maximum allowance: 80 ppb
• EWG recommended maximum: 0.15 ppb
• San Francisco maximum contaminant level: 41.1 ppb

Chromium (Hexavalent)

Chromium is another common contaminant found in U.S. water supplies. It can occur naturally but is also an industrial pollutant. Although it’s known to be a carcinogen, this contaminant is still unregulated by the EPA.

Chromium levels in San Francisco water have exceeded what the EWG recommends for safety by 4.5 times:

• EPA maximum allowance: No legal limit
• EWG recommended maximum: 0.02 ppb
• San Francisco maximum detected level: 0.0906 ppb

Carbon Tetrachloride

Carbon tetrachloride is a synthetic compound that was commonly used as a solvent and cleaning agent. It is a volatile organic compound known to have harmful effects on the liver, kidneys, and central nervous system. Additionally, it is a probable human carcinogen. This chemical is now largely restricted due to its ozone-depleting properties and health risks.

Levels of carbon tetrachloride in San Francisco water have exceeded what the EWG recommends for safety by 7.3 times:

• EPA maximum allowance: 5 ppb
• EWG recommended maximum: 0.1 ppb
• San Francisco maximum contaminant level: 0.725 ppb

Does San Francisco Have Hard Water?

With a little over 9 parts per million (ppm) of dissolved minerals, San Francisco has moderately hard water. Water hardness is measured by the concentrations of dissolved minerals like calcium and magnesium in water. The higher the concentration, the harder the water.

When water passes over soil and rocks, it dissolves minerals and carries them along until depositing them elsewhere. While consuming hard water isn’t considered to have negative health effects, when hard water minerals deposit themselves in your plumbing and on your surfaces, they can wreak havoc. Hard-to-clean limescale gives bacteria a place to grow, and the minerals mix with soap to create soap scum on your skin and hair so you never get fully clean.

If you’re dealing with hard water in San Francisco, a high-quality water softener will fix the issue.

Does San Francisco Add Fluoride to Drinking Water?

Yes, San Francisco does fluoridate their water as part of the water treatment process. Like many American water utilities, San Francisco adds fluoride to their tap water as a public health measure. Fluoride has been shown to strengthen and rebuild tooth enamel, which decreases the instances of dental cavities.

Some people welcome this benefit while others would rather control their own fluoride use. If you’d like to remove fluoride from your water, you should be aware that most water filters or boiling water will not remove fluoride. For that, you’ll need a high-quality reverse osmosis filtration system.

Get the Best Quality Water in Your San Francisco Home

San Francisco is a beacon for environmental sustainability and cultural diversity, but even this progressive city faces challenges with water resources. Issues like aging infrastructure, contamination from industrial pollutants, and climate change affect San Francisco water quality.

If you want the best-tasting clean water straight from your San Francisco tap, HomeWater can help. HomeWater's UPSTREAM 4-Stage Whole Home Water Filters can improve your water quality by removing impurities like sediment, chloramines, DPBs, PFAS, microplastics, heavy metals like chromium, and more.

Elevate your San Francisco water experience with HomeWater.