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San Diego Water Quality City View Downtown

September 2023

Beyond the Surf: A Look at San Diego Water Quality

If you’ve spent even a day in San Diego, California, you understand what all the fuss is about. The city has one of the best climates in the world, a magnet that attracts a lot of people. As the eighth most populated city in the United States, the city of San Diego is home to over 1.3 million people, with another 2 million residing in greater San Diego County.

San Diego is not just celebrated for its climate though. The city boasts an incredibly rich history, a thriving economy, and a concentration of natural beauty that seems almost unfair for one location. With over 70 miles of coastline, this Southern California town delights beachgoers and simultaneously offers substantial economic opportunities through trade and tourism. In fact, the city's dynamic economic environment has earned it a ranking as the third best place in the country to launch a new business.

But water resources in San Diego aren't just about beaches and commerce. Water is crucial to the health and hygiene of the millions of people who call the county of San Diego home.

In this article we’re going to dive deep to find out the good and the bad of San Diego water quality. We’ll look at where San Diego water comes from, what’s in it, and let you know if there’s anything you need to be concerned about.

Where Does San Diego Water Come From?

With so much coastline, it can feel like water is everywhere in San Diego. But even with the largest desalination project in the country pumping out 50 million gallons from the Pacific per day, San Diego still doesn't have nearly enough freshwater to meet the demands of its large population. That means about 90% of the water San Diegans drink is imported by the San Diego Water Authority (SDWA).

The SDWA brings in most of its water untreated from the Colorado River and the State Water Project. That raw water is then sent to the Miramar Treatment Plant, the Alvarado Treatment Plant, or the Otay Treatment Plant where it’s processed for use.

The other 10% of the drinking water coming into your home is purchased from the Metropolitan Water District’s Skinner Water Treatment Plant, the County Water Authority’s Twin Oaks Valley Water Treatment Plant, and the Carlsbad Desalination Plant.

How Does San Diego Treat Its Water?

San Diego water quality is important to all citizens who rely on it. In order to make it the best it can be, San Diego relies on a multi-stage treatment process, which includes:

  • Coagulation: As water rushes into the treatment plant, coagulants are mixed in that change the electrostatic charge of particles in the water, making contaminants more likely to clump together.
  • Flocculation: Once mixed with coagulants, the water is slowly mixed while the particles in the water come together in clumps called floc.
  • Sedimentation: Once the floc has formed, it's allowed to sink to the bottom. The clean water at the top is taken on to the primary disinfection stage.
  • Primary disinfection: Depending on the water source, it is then disinfected using either ozone or chlorine to kill pathogens that would otherwise make people sick.
  • Filtration: While most of the big particles are removed early on, this filtration stage lowers turbidity to make sure your drinking water is crystal clear.
  • Secondary disinfection: Once filtered the water heads to storage tanks before being delivered. To ensure the water remains safe from pathogens during storage and delivery, chloramines are added to the water. The pH of the water is also adjusted to decrease pipe corrosion.

Water samples are taken and tested regularly. Based on the water quality test results adjustments can be made to the treatment methods as well as where water is imported from.

Is San Diego Water Quality Good?

Since 2018, over 100 billion gallons of toxic effluent from sewage spills have flowed through the Tijuana River. Much of it has crossed the U.S.-Mexico border, causing harm to San Diego’s coast. After months of beach closures and lifeguards warning swimmers of the health risks of going in the water, in June 2023, San Diego declared a state of emergency.

Water pollution in the Tijuana River Valley has left the south side of Imperial Beach closed for over a year and a half. While other local beaches have fared better, bacteria levels in many of them continue to test considerably higher than health standards would deem safe.

While county beaches are struggling with cross-border pollution, wastewater treatment plants and other water systems in the city are aging. Recent large storms have proven a challenge for the infrastructure and line breaks are becoming more frequent. The city recently agreed to a $4.6 million fine after 11 million gallons of wastewater found its way into the Sweetwater River.

Is San Diego Tap Water Safe to Drink?

According to the San Diego Water Quality Report and the U.S. Environmental Protection Agency (EPA), San Diego tap water is safe to drink. It’s important to note that meeting regulatory standards doesn’t always mean water is safe, though.

Since 1974, the EPA has set minimum quality standards for drinking water quality for all public water suppliers. Today this means having enforceable standards for 92 different substances commonly found in U.S. water sources.

While these standards are important, there are thousands of potential contaminants in water that aren't tested for. Contaminants like microplastics, which are found in water supplies across the globe, have no limits placed on them because testing is still in its infancy.

Other known contaminants like PFAS have been known to cause health problems for decades. Companies have been voluntarily phasing them out for over 20 years, but it’s taken until 2023 for the EPA to suggest enforceable limits in your drinking water.

According to D.C.-based water watchdog, the Environmental Working Group (EWG), if these new standards become law, it will be the first change in water regulations in over 20 years, even as our understanding of many contaminants and their dangers has changed.

Simply put, regulation often lags behind science, and the scientific community is learning more about new contaminants every year. According to the EWG, many current regulations are out of date and not in line with what scientists currently believe safe levels are.

Let’s look at some of the chemicals found in San Diego’s water that are within legal limits but questionable based on modern science.

What Contaminants Are in San Diego’s Water?

One of the problems San Diego water quality faces is disinfection byproducts (DBPs). When chlorine and chloramines interact with organic matter, they can create carcinogenic DBPs. There are also problems with elevated levels of arsenic, chromium, radium, and uranium.

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 Diego water have exceeded what the EWG recommends for safety by 96 times:

  • EPA maximum allowance: 60 parts per billion (ppb)
  • EWG recommended maximum: 0.1 ppb
  • San Diego maximum contaminant level: 9.6 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 Diego water have exceeded what the EWG recommends for safety by 302 times:

  • EPA maximum allowance: No legal limit
  • EWG recommended maximum: 0.06 ppb
  • San Diego maximum contaminant level: 18.1 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 Diego water have exceeded what the EWG recommends for safety by 231 times:

  • EPA maximum allowance: 80 ppb
  • EWG recommended maximum: 0.15 ppb
  • San Diego maximum contaminant level: 36.1 ppb


Arsenic is carcinogenic and is known to cause damage to the brain, central nervous system, skin, and blood vessels. Arsenic is a common contaminant in U.S. public drinking water because it can occur naturally in groundwater.

Arsenic levels in San Diego water have exceeded what the EWG recommends for safety by 23 times:

  • EPA maximum allowance: 10 ppb
  • EWG recommended maximum: 0.004 ppb
  • San Diego maximum detected level: 0.0901 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 Diego water have exceeded what the EWG recommends for safety by 2.1 times:

  • EPA maximum allowance: No legal limit
  • EWG recommended maximum: 0.02 ppb
  • San Diego maximum detected level: 0.0421 ppb


Radium is a radioactive heavy metal found both in nature and as a byproduct of oil and gas production. Radium is a known carcinogen. Legal limits for radium are measured in picocuries per liter (pCi/L), which is a measure of radioactivity.

Radium levels in San Diego water have exceeded what the EWG recommends for safety by 7.9 times:

  • EPA maximum allowance: 5 pCi/L
  • EWG recommended maximum: 0.05 pCi/L
  • San Diego maximum detected level: 0.4 pCi/L


Uranium is a radioactive heavy metal found both in nature and as a byproduct of oil and gas production. Uranium is a known carcinogen.

Uranium levels in San Diego water have exceeded what the EWG recommends for safety by 4.2 times:

  • EPA maximum allowance: 20 pCi/L
  • EWG recommended maximum: 0.43 pCi/L
  • San Diego maximum detected level: 1.81 pCi/L

Is San Diego Tap Water Hard or Soft?

San Diego has some of the hardest water in the United States. Ranging from 16 to 18 grains per gallon or 272 to 284 ppm, the tap water in San Diego is considered extremely hard.

Water is considered hard when it contains a high concentration of dissolved calcium and magnesium. While these aren’t dangerous to ingest, they can wreak havoc on your pipes, surfaces, clothing, water-using appliances, and your skin.

To get rid of hard water, you’ll either need to use a water softener or a salt-free water conditioner.

Does San Diego Add Fluoride to Their Water?

Yes, San Diego does add fluoride to their water. The California Department of Health mandates that large water suppliers add fluoride to their water supply as a public health measure. Fluoride is known to protect tooth enamel and reduce cavities.

Some people are quite happy with the use of fluoride in their water but if you would rather remove it from your water, keep in mind that regular activated carbon filters will not remove it. Instead, you’ll need a reverse osmosis filter.

Get the Best Quality Water in Your San Diego Home

The city of San Diego is easily one of the best cities in the U.S. to live and work in, but when it comes to the water quality, some work needs to be done. With public beach closings becoming normal and aging wastewater infrastructure releasing sewage into local waters, the small amount of drinking water the oceanside city has left could be in jeopardy.

If you want the best tasting water from your tap no matter what, HomeWater can help. Our UPSTREAM 4-Stage Whole Home Water Filter will deliver clean, crisp water to every faucet in your home. It will remove pollutants like dirt, rust, chlorine, DPBs, heavy metals, PFAS, microorganisms, and more. Add a water softener to get rid of that San Diego hard water for good.

With our HomeWater 4-Stage Reverse Osmosis Under Counter Water Filter, you’ll get premium water right from your kitchen tap. Reduce lead, fluoride, microplastics, chloramines, and disinfection byproducts for the most delicious, high-quality water you can get in San Diego.

You’ll be able to taste the difference with HomeWater filters.

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