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Los Angeles Water Quality: What You Need to Know in 2025
Los Angeles has it all—sunshine, a buzzing city life, and the Hollywood dream—but what about the big mysteries of the beloved city? The tap water. It’s easy to assume it’s perfectly safe and it’s such a part of daily lives, it’s rare to actually think about how our tap water is safe.
While the Los Angeles Department of Water and Power (LADWP) works hard to meet safety standards, there’s more to the story. Contaminants like lead, arsenic, and pharmaceutical medications can still sneak into your water, especially when it travels through older pipes.
So, where does LA’s water come from, and what’s being done to keep it clean? More importantly, what can you do to ensure your home's water is as safe as possible?
In this guide, we’ll break it all down:
- Where LA gets its water
- What the Annual Water Quality Report reveals
- Why groups like the Environmental Working Group (EWG) push for even stricter standards
- How contaminants like lead, TTHMs, and arsenic can affect your health
- And most importantly—how in-home water filters can help you take control.
If you’re curious about what’s really in your water—and how to fix it—you’re in the right place.
01 | Who Regulates Los Angeles Drinking Water?

The regulation of Los Angeles’s drinking water is a collaborative effort involving federal, state, and local agencies. Each plays a critical role in ensuring that water delivered to homes meets strict safety standards.
Los Angeles drinking water is regulated by a combination of federal, state, and local agencies to ensure safety and quality:
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U.S. Environmental Protection Agency (EPA):
Sets the national Maximum Contaminant Levels (MCLs) through the Safe Drinking Water Act to protect public health. -
California State Water Resources Control Board (SWRCB):
Enforces stricter state-level standards, often more protective than federal regulations, and monitors emerging contaminants like PFAS. -
Office of Environmental Health Hazard Assessment (OEHHA):
Sets Public Health Goals (PHGs)—health-based benchmarks that go beyond legal limits to reduce long-term health risks. - Los Angeles Department of Water and Power (LADWP):
- Tests for over 100 contaminants regularly.
- Treats, monitors, and delivers water to millions of residents.
- Publishes the Annual Water Quality Report for transparency and accountability.
By working together, these agencies ensure Los Angeles drinking water meets safety standards.
02 | Where Does Los Angeles Get Its Water?

Los Angeles's water supply is as diverse as the city itself, with water coming from multiple sources spread across hundreds of miles. This intricate system blends imported and local water to meet the needs of millions of residents.
Los Angeles relies on a mix of local and imported sources to meet its water needs:
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Los Angeles Aqueduct:
Supplies about 30% of the city’s water, sourced from snowmelt in the Eastern Sierra Nevada. -
Groundwater:
Provides 10–15% of LA’s water, mostly from the San Fernando Valley Aquifer, though some areas face contamination challenges. -
Metropolitan Water District (MWD):
About 73% of the city’s water is imported from the Colorado River and Northern California’s State Water Project, though these sources often have higher mineral content. -
Recycled Water:
Used for irrigation and industrial purposes, recycled water is part of LA’s sustainability strategy, with plans to expand its role in the future. To learn more about how California is turning wastewater into a valuable resource, check out our blog: California’s New Water: How Wastewater Impacts Your Family -
Rainwater and Stormwater Capture:
While still a smaller contributor, stormwater projects help replenish groundwater and reduce urban runoff.
Shop Wastewater Filter Systems
03 | Los Angeles City’s Annual Water Quality Report

Every year, the LADWP publishes an Annual Water Quality Report, providing an inside look at the city’s water safety and compliance with federal and state standards. The 2023 report highlights extensive testing for over 100 contaminants, offering reassurance about water safety while underscoring areas for ongoing improvement.
Before we get started, we use a few measurements that not everyone sees all the time.
Parts per billion (ppb) and parts per million (ppm) describe how small that amount is compared to the whole pool of water. Imagine you have a giant swimming pool filled with water. Now, let’s say you add a tiny bit of something (like food coloring) to that pool.
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Parts per billion (ppb):
If you added just 1 drop of food coloring to a pool that had a billion drops of water, that’s 1 part per billion. It’s a super tiny amount—like finding 1 single penny in a pile of a billion pennies. -
Parts per million (ppm):
Now, if the pool only had a million drops of water and you added 1 drop of food coloring, that’s 1 part per million. It’s a bigger amount than ppb but still pretty small—like finding 1 penny in a pile of a million pennies.
Things like lead or nitrates in water are often measured in ppb because even tiny amounts matter for your health.
Key Highlights from the 2023 Report
Compliance with EPA Standards
The report confirms that all regulated contaminants in Los Angeles water meet or exceed EPA’s Maximum Contaminant Levels (MCLs), ensuring the water is legally safe to drink.
- Arsenic:
- Average: 2.4 parts per billion
- EPA Limit: 10 ppb
Arsenic levels are well within federal guidelines, though long-term exposure to even low levels remains a concern for groups like the EWG.
- Lead (at-the-tap):
- 3 out of 105 samples exceeded the federal action level of 15 ppb.
While most samples fell within safe levels, this highlights the risk of household plumbing corrosion in older homes and schools.
- Haloacetic Acids (HAA5):
- Average: 13.9 ppb
- EPA Limit: 60 ppb
These byproducts of water disinfection remain within safe limits, but minimizing their formation is an ongoing priority.
- Total Trihalomethanes (TTHMs):
- Average: 37.9 ppb
- EPA Limit: 80 ppb
TTHMs, another byproduct of chlorine disinfection, remain below the federal threshold but continue to be monitored for their potential health risks.
Sources of Contaminants
LADWP’s testing identifies several sources of contaminants, including:
- Natural Deposits: Arsenic and uranium from local groundwater.
- Disinfection Byproducts: TTHMs and HAA5 form when chlorine reacts with organic matter in water.
- Runoff and Industrial Pollution: Nitrates from fertilizers and potential pollutants from urban runoff.
Water Hardness
Water hardness levels in Los Angeles range between 102–160 ppm (aka hard water) depending on the source. While not a health risk, hard water can cause scaling in appliances and affect taste.
You can view your water hardness levels by buying a water hardness test or finding a water hardness analysis online.
LADWP’s Commitment to Transparency and Safety
The annual report is part of LADWP’s broader commitment to transparency, ensuring residents have access to detailed information about their drinking water. Key initiatives include:
- Regular Monitoring: Testing for contaminants at treatment plants, distribution points, and at-the-tap.
- Public Education: Encouraging residents to flush pipes and consider in-home water filters for added safety.
- Future Goals: Expanding water recycling programs and improving infrastructure to reduce contaminant risks.
What the Report Means for You
While the 2023 report confirms that Los Angeles water meets regulatory standards, some contaminants, like lead and disinfection byproducts, highlight the need for proactive measures by residents:
- Install Filters: NSF-certified filters, like reverse osmosis systems, can effectively remove contaminants like arsenic and lead.
- Stay Informed: Review LADWP’s annual reports to understand what’s in your water and how it’s being treated.
- Monitor Your Pipes: Older homes with lead plumbing may require regular flushing or professional assessment.
By staying informed and taking small steps to address potential risks, residents can ensure their water remains as safe and clean as possible.
04 | Environmental Working Group Water Quality Report

The LADWP ensures water complies with federal standards while the Environmental Working Group (EWG) provides an alternative evaluation. The EWG applies stricter, health-based guidelines to water contaminants, raising awareness about potential risks even when levels are within legal limits.
The EWG’s stricter standards often contrast with EPA regulations:
- Arsenic and bromate levels, though compliant with EPA standards, exceed EWG’s health-based guidelines.
- EWG highlights areas for improvement, encouraging stronger public awareness and advocacy for improved water treatment.
9 substances greatly exceed the EWG’s recommended guidelines:
- Arsenic: 430x
- Bromate: 7.3x
- Chromium (hexavalent): 29x
- Haloacetic acids (HAA5): 103x
- Haloacetic acids (HAA9): 184x
- Nitrate: 12x
- Nitrate and nitrite: 7.6x
- Total trihalomethanes (TTHMs): 177x
- Uranium: 7x
Other contaminants detected at lower concentrations include
- 1,1-Dichloroethane
- 1,2-Dichloroethane
- 1,4-Dioxane
- Aluminum
- Barium
- Bromide
- Bromochloromethane
- Chlorate
- Chlorodifluoromethane
- Chromium (total)
- Fluoride
- Manganese
- Molybdenum
- Nitrite
- O-toluidine
- Selenium
- Strontium
- Tetrachloroethylene (perchloroethylene)
- Trichloroethylene
- Trichlorofluoromethane
- Vanadium
How Does EWG Differ from EPA?
- The EPA's standards (Maximum Contaminant Levels, MCLs) are based on a balance of safety, cost, and technological feasibility.
- The EWG guidelines, on the other hand, are health-focused benchmarks based on the latest scientific research, often much stricter than federal standards.
- For example:
- Arsenic (EPA Limit: 10 ppb vs. EWG Guideline: 0.004 ppb)
- TTHMs (EPA Limit: 80 ppb vs. EWG Guideline: 0.15 ppb)
The EWG water quality report is a valuable resource for those seeking a deeper understanding of what’s in Los Angeles’s drinking water. While the water meets legal limits, adopting additional measures, like in-home water filters, ensures peace of mind and protection against potential long-term risks.
05 | Top Contaminants Threatening Los Angeles City Water Quality

Most people don’t think about the contaminants in their water that could impact their health. The Los Angeles Department of Water and Power monitors these substances and meets federal guidelines, but they still raise important questions about long-term exposure risks.
-
Arsenic: The Silent Intruder
What is it?
Arsenic is a naturally occurring element found in groundwater. It can also enter the water supply through industrial and agricultural pollution.
How does it affect your health?
- Short-term exposure: Generally not a concern at low levels.
- Long-term exposure: Even small amounts over time can lead to serious health problems, including skin damage, developmental issues, and an increased risk of cancer.
In Los Angeles, arsenic levels average 2.4 ppb, well below the EPA limit of 10 ppb, but still a concern for those relying on water for long-term use.
-
Haloacetic Acids (HAA5 and HAA9)
What are they?
Haloacetic acids (HAA5 and HAA9) are disinfection byproducts formed when chlorine or other disinfectants react with organic materials in the water.
- HAA5 refers to five specific acids monitored by the EPA.
- HAA9 is a broader group that includes additional acids, gaining attention for their potential health impacts.
How do they affect your health?
- Cancer Risks: Long-term exposure to HAA5 and HAA9 has been linked to an increased risk of bladder and colorectal cancer.
- Developmental Issues: Exposure during pregnancy may affect fetal development.
In 2023, HAA5 levels in Los Angeles averaged 13.9 ppb, well below the federal limit of 60 ppb. While this meets EPA standards, experts like the Environmental Working Group (EWG) argue that stricter limits should be in place to protect public health.
-
TTHMs (Total Trihalomethanes): A Chlorination Challenge
What are they?
TTHMs are another disinfection byproduct formed when chlorine reacts with natural organic matter in the water.
How do they affect your health?
- Short-term exposure: Can cause skin irritation and respiratory issues, especially during showers where TTHMs can be inhaled.
- Long-term exposure: Linked to liver, kidney, and central nervous system damage, as well as an increased risk of cancer.
In Los Angeles, TTHM levels averaged 37.9 ppb, below the EPA limit of 80 ppb, but 177 times higher than the EWG’s health guideline.
-
Bromate: A Byproduct of Ozone Treatment
What is it?
Bromate is a disinfection byproduct that forms when ozone, used to treat water, reacts with naturally occurring bromide in the source water. Ozone is an effective disinfectant, but this reaction introduces bromate into the treated water.
How does it affect your health?
- Long-term exposure: Increases the risk of cancer and can cause kidney damage.
- Short-term effects: High levels can irritate the stomach and intestines.
Monitoring and Regulation:
- The EPA’s Maximum Contaminant Level (MCL) for bromate in drinking water is 10 parts per billion (ppb).
- Water providers use precise treatment techniques to keep bromate levels within allowable limits while ensuring water is effectively disinfected.
LADWP’s Efforts:
LADWP employs ozone as part of its disinfection process while carefully monitoring and maintaining bromate levels below regulatory limits.
-
Chromium (Hexavalent): A Carcinogenic Industrial Pollutant
What is it?
Chromium (hexavalent), or Cr6, is an industrial chemical used in manufacturing, known for its contamination of water supplies through industrial runoff.
How does it affect your health?
- Cancer risks: Linked to cancers of the lung, stomach, and intestines.
- Other effects: Long-term exposure can harm the liver, kidneys, and cause skin irritation.
Monitoring and Regulation:
- California’s Public Health Goal (PHG) for Cr6 is set at an extremely low 0.02 ppb, reflecting health-based benchmarks.
- No federal MCL specifically addresses Cr6; it is currently regulated under the broader total chromium standard of 100 ppb.
LADWP’s Efforts:
Groundwater supplies are monitored for chromium (hexavalent). While levels are below the federal standard for total chromium, ongoing efforts aim to address community concerns and comply with California’s stricter guidelines.
-
Uranium: A Naturally Occurring Radioactive Element
What is it?
Uranium is a radioactive metal found naturally in rocks and soil. It can leach into groundwater and enter drinking water supplies, particularly in areas with uranium-rich geological formations.
How does it affect your health?
- Kidney damage: Uranium can harm kidney function with prolonged exposure.
- Radiation risks: Even small amounts of uranium contribute to overall radiation exposure, which may very likely increase cancer risk over time.
Monitoring and Regulation:
- Groundwater samples are tested regularly for uranium. Current levels average 3.5 pCi/L, which is seven times above the EWG’s limit, yet nearly 7x below the legal limit of 20 pCi/L.
-
Lead: A Risk from Aging Plumbing
What is it?
Lead typically enters drinking water not from the water source, but through household plumbing systems. Older homes with lead pipes, solder, or fixtures are at higher risk, as lead can leach into water when pipes corrode.
How does it affect your health?
- Children: Even low levels of lead exposure can cause cognitive impairment, reduced IQ, and developmental delays.
- Pregnant Women: Lead can cross the placenta, potentially harming fetal development.
- Adults: Long-term exposure may lead to kidney damage, high blood pressure, and cardiovascular issues.
Current Monitoring:
In LADWP’s 2023 testing, 3 out of 105 tap water samples exceeded the EPA’s action level of 15 parts per billion (ppb). While most samples were below this threshold, homes with older plumbing systems remain at risk.
VIII. Nitrate: A Contaminant from Agricultural Runoff
What is it?
Nitrate enters water supplies primarily through agricultural runoff, fertilizers, and septic systems. It can seep into both surface water and groundwater sources.
How does it affect your health?
- Infants: Nitrate can cause “blue baby syndrome”, a condition that reduces oxygen delivery in the bloodstream, potentially leading to severe illness or death.
- Adults: Long-term exposure has been linked to an increased risk of cancer and thyroid problems.
Current Monitoring:
While nitrate levels in Los Angeles water are below the EPA’s limit of 10 mg/L, they remain 12 times higher than the EWG’s stricter health guideline, signaling potential risks for sensitive populations.
06 | Health Risks of Contaminants in Unfiltered Water in Los Angeles

Even though Los Angeles water meets federal and state safety standards, unfiltered tap water can still contain trace amounts of contaminants that may pose health risks over time. Long-term exposure, even at low levels, can have cumulative health effects, particularly for children, pregnant women, and individuals with compromised immune systems.
Concerns like
- Stomach cancer
- Kidney cancer
- Radiation exposure
- Thyroid disease
- Liver damage
- Reproductive issues
- Developmental delays in children
- Birth defects
- Heart problems
By understanding these risks and installing reverse osmosis or activated carbon filtration systems, residents can take control of their water quality, ensuring it’s safer for drinking, cooking, and bathing.
07 | Shocking Statistics of Lead Contamination In Los Angeles Schools

Recent water quality tests in Los Angeles schools have raised serious concerns about lead contamination. While the LADWP ensures that water leaving treatment plants meets EPA standards, issues often arise once water travels through aging plumbing systems, especially in older buildings like schools.
During 2023 testing, lead levels exceeded the federal action level of 15 ppb in several locations. This is especially alarming because children are more vulnerable to lead exposure. Even small amounts of lead can cause irreversible developmental delays, cognitive impairments, and behavioral problems.
Investing in plumbing upgrades is the long-term fix Los Angeles needs to eliminate this problem. Until then, families can protect their children with reliable point-of-use water filters for drinking water.
08 | Treating Los Angeles Drinking Water

Providing clean drinking water to millions of Los Angeles residents requires advanced treatment processes by LADWP to meet EPA standards. While water leaving treatment plants is carefully monitored, aging infrastructure can still affect its quality by the time it reaches your tap.
Key Treatment Steps
-
Filtration:
Water is filtered to remove:
- Turbidity: Cloudiness caused by sediment particles.
-
Organic Matter: Prevents formation of disinfection byproducts like TTHMs and HAA5.
The Los Angeles Aqueduct Filtration Plant plays a major role in treating water from the Eastern Sierra Nevada.
-
Disinfection:
LADWP uses two main methods to kill harmful bacteria and viruses:
- Chlorination: Chlorine is added to eliminate pathogens.
- Ozonation: Ozone treatment reduces contaminants and byproducts like bromate.
By addressing these post-treatment issues, LADWP continues to improve water quality for residents across Los Angeles.
09 | Testing and Monitoring Los Angeles City Water Quality
LADWP ensures Los Angeles water meets EPA standards and stricter California regulations through rigorous testing of over 100 contaminants, keeping water safe from the source to the tap.
What Does LADWP Test For?
LADWP conducts comprehensive testing for a wide range of contaminants, including:
- Heavy Metals: Lead, arsenic, copper
- Disinfection Byproducts: TTHMs, HAA5
- Microbial Contaminants: Coliform bacteria
- Chemicals & Minerals: Nitrates, fluoride, calcium, magnesium
- Emerging Contaminants: PFAS and other unregulated chemicals
Fun Fact: |
In 2023, lead levels exceeded the federal action level in 3 out of 105 tap water samples, highlighting the risks posed by aging household pipe |
Emerging Contaminants in LA
LADWP proactively monitors PFAS and other unregulated contaminants through federal programs like UCMR, helping set future safety standards.
Where and How Is Water Tested?
LADWP monitors water quality at multiple stages:
-
Treatment Plants:
Water is thoroughly tested as it leaves treatment facilities, ensuring it meets EPA safety standards. -
Distribution System:
Regular testing occurs at reservoirs, storage tanks, and distribution pipes to identify any contamination risks. -
Tap Water Testing:
Samples are collected from homes, schools, and businesses to monitor contaminants like lead caused by aging plumbing systems.
To ensure safe water delivery, LADWP follows:
- EPA Guidelines: Compliance with Maximum Contaminant Levels (MCLs) set by the Environmental Protection Agency.
- California Regulations: Stricter state benchmarks for contaminants, reflecting growing concerns about long-term health effects.
The results are summarized annually in LADWP’s Water Quality Report, which provides a detailed breakdown of contaminant levels and compliance.
10 | Should Los Angeles Residents Use In-home Water Filters?

The LADWP works hard to ensure the city’s water meets EPA safety standards, but some contaminants can still pose risks once the water reaches your home. Issues like lead, arsenic, and disinfection byproducts are concerns that every homeowner should be aware of. Installing an in-home water filter can provide cleaner, safer water for you and your family.
Installing an in-home water filter provides several benefits:
- Health Protection: Filters remove harmful contaminants like lead, arsenic, and disinfection byproducts.
- Better Taste and Odor: Activated carbon filters reduce chlorine, improving the taste and smell of water.
- Cost Savings: Investing in a filtration system eliminates the recurring cost of bottled water. Why? Because the water tastes better.
- Peace of Mind: You gain control over your home’s water quality, ensuring it’s cleaner and safer.
The Best Filtration Options for Los Angeles Homes
- Reverse Osmosis Systems
Removes lead, arsenic, disinfection byproducts, and other contaminants for complete purification.
- Activated Carbon Filters
Reduces chlorine, TTHMs, and HAA5 while improving taste and odor.
- Whole-House Water Softeners
Reduces hard water minerals, protecting your appliances, plumbing, and skin.
Explore Water Softener Systems
Take Control of Your Water Quality
While LADWP works to provide clean water, contaminants from aging infrastructure or disinfection processes can still impact your water quality at home. Installing a reliable in-home filtration system—whether it’s a reverse osmosis system for advanced purification, an activated carbon filter for taste, or a water softener for hard water—gives you the peace of mind that your water is safe and clean.