Monterey Park water quality report: is your tap water safe, and how hard is it?
Is Monterey Park tap water safe, and how hard is it? Plain-English 2025 results and what they mean for your faucets, water heater and pipes.
Updated · 3 min read
Bottom line
Short answer: the Monterey Park water quality report for 2025 says the city's water met every state and federal drinking-water standard. It is also very hard: about 20.8 grains per gallon from the city's own wells and 14.3 from the water the city buys. Hard water won't make you sick, but it leaves crust on faucets, scale inside your water heater and spots on glass.
Contents
Your water at a glance
Here are the seven things homeowners ask about most, with numbers from the city's 2025 report. "ND" means not detected.
| What you care about | What the report found | Legal limit | What it means for you |
|---|---|---|---|
| Safe to drink? | The city says it met all state and federal standards | Every result is under its limit | Yes, by the legal standard. See the next section for the health-goal side |
| Hardness (scale buildup) | City wells 356 mg/L (20.8 grains). Bought water 246 mg/L (14.3 grains) | None, hardness is not a health issue | Very hard. Expect crust, spots and heater scale |
| Dissolved minerals (TDS) | City wells 502 ppm. Bought water 352 ppm | 1,000 ppm, a taste-and-look limit | Under the limit. This one is about taste and spots, not health |
| Disinfectant (chlorine) | 0.73 ppm average at the tap | 4.0 ppm | Chlorine, not chloramine. Some people notice the taste |
| Nitrate | City wells 2.9 ppm. Bought water 2.44 ppm | 10 ppm | Well under the limit |
| Arsenic | City wells 0.66 ppb average, highest 3.1. Bought water ND | 10 ppb | Under the limit, above California's health goal of 0.004 ppb |
| PFAS | City sources: PFBA 5.5, PFBS 2.0, PFHxA 2.4 parts per trillion on average. Bought water ND | 4.0 ppt for PFOA and PFOS, due 2029 | PFOA was not detected on average. PFOS is not on the city's detection list |
Hardness is the number that matters most for your house. It is mostly calcium and magnesium, and it is the reason you see white crust where water dries.
Is it safe to drink?
According to the city, yes. The report says the water met or surpassed all state and federal standards, and no result in its tables is over a legal limit.
There are two yardsticks in a water report. The legal limit is the most the state allows. The health goal is a lower level set by California, where there is no known risk. Limits are set as close to the goals as is practical, so the two rarely match.
Arsenic shows how both can be true. The city wells average 0.66 ppb: about 15 times under the legal limit of 10 ppb, and about 165 times over the 0.004 ppb health goal. Chromium-6 and uranium are in the same spot, under the limit and over the goal.
Tap tests at 37 homes in the 2024 round found no home over the action level for copper or for the metal old solder and service lines can add. The highest results were 0.97 ppm copper and 5.6 ppb for that metal, against action levels of 1.3 ppm and 15 ppb.
What you'll notice at home
Hard water mostly shows up as cleaning chores and wear on equipment:
- White, crusty buildup on faucets, aerators and showerheads. Our guide to hard water buildup on faucets in Monterey Park shows how to deal with it.
- Spots on glasses, dishes and shower doors.
- Scale on the bottom of a tank water heater. A.O. Smith says it acts like a blanket, so the heater runs longer, costs more to run and may rumble.
- Scale inside a tankless heater too. See tankless water heaters and hard water.
- A chlorine taste or smell in some glasses of water.
What helps
| If you want to fix | What helps | Where to start |
|---|---|---|
| Crust, spots and scale | A water softener. The EPA says it swaps sodium for the calcium and magnesium that make water hard | Softener sizing for Monterey Park and our water softener service |
| Heater scale and rumbling | Softer water going in, plus a heater that is checked, including the anode rod | Our water heater service |
| Chlorine taste | A carbon filter tested to NSF/ANSI 42, says the EPA | Plan it into the order with a softener |
| Arsenic, chromium-6, nitrate or uranium on your mind | Decide the goal first. The EPA says no single system removes everything, and a softener won't remove these | Call and talk it through before you buy |
A softener solves a hardness problem, not a drinking-water problem. Be wary of anyone who says one box does both.
When to call
- Crust keeps coming back after you clean your faucets and showerheads.
- Your water heater rumbles, pops or runs out of hot water sooner than it used to.
- You are deciding whether to put in a softener, and want it sized to your address.
- You want a second set of eyes on a filter plan for drinking water.
Getting help in Monterey Park
Hard water is a fact of life in Monterey Park. For this job, start with our water softener service page, then send us a note or text (310) 628-9399.
Before you call
Is Monterey Park tap water safe to drink?
The city's 2025 report says the water met all federal and state standards, and no result is over a legal limit. Some contaminants, such as arsenic and chromium-6, are under the limit but above California's health goals.
Is Monterey Park water hard?
Yes, very. The city's wells measure 356 mg/L (20.8 grains per gallon) and the water it buys measures 246 mg/L (14.3 grains). The U.S. Geological Survey calls anything above 180 mg/L very hard.
Does Monterey Park water have PFAS?
The city's own sources show three PFAS on average: PFBA, PFBS and PFHxA, at 2 to 6 parts per trillion. PFOA was not detected on average, and none was detected in the bought water.
Does Monterey Park use chlorine or chloramine?
Chlorine. The city says its water is disinfected with chlorine, and the report's disinfectant row averages 0.73 ppm against a limit of 4.0.
Will a water softener remove arsenic or chromium-6?
No. The EPA describes a softener as swapping sodium for calcium and magnesium. Removing arsenic or chromium-6 takes a different kind of treatment, and no single system removes everything.
Why do EWG's numbers look worse than the city's?
EWG compares results with stricter health benchmarks and uses older data, 2014 to 2023. The city's report compares them with legal limits. Both can be accurate.
Sources and notes
Where the numbers come from
Every number above is from the City of Monterey Park's 2025 water quality report, also called a Consumer Confidence Report. The city's wells draw from the Main San Gabriel Groundwater Basin, and the city also buys water from San Gabriel Valley Water Company. The report does not say how much of each source reaches your street, so your address could be closer to either number. The city's water quality page says the water is disinfected with chlorine.
Treatment and 1,4-dioxane
Past industrial discharge has contaminated groundwater in parts of the Main Basin, so the city treats its well water with ultraviolet advanced oxidation and two carbon units. The report also covers 1,4-dioxane, a solvent with no federal or state legal limit. The state's notification level has been 1 microgram per liter since 2010. Some city wells tested above it, and in 2025 the treated wells showed none.
| Measure | City wells | Bought water | Legal limit | Health goal |
|---|---|---|---|---|
| Chromium-6, ppb | 1.79 | 3.33 | 10 | 0.02 |
| Uranium, pCi/L | ND | 6.8 | 20 | 0.43 |
| Fluoride, ppm | 0.7 | 0.6 | 2.0 | 1 |
| Specific conductance, uS/cm | 801 | 572 | 1,600 | none |
Tap tests, PFAS and data windows
Tap sampling happens every three years, so the report shows the 2024 round at 37 homes. Copper's 90th percentile was 0.33 ppm. The metal from old solder and service lines was not detected at the 90th percentile. The report says the city missed its October 16, 2024 deadline for its service line material inventory, submitted it June 23, 2025 and notified customers July 25, 2025.
The PFAS results come from federal testing that the report says runs 2023 to 2025. PFHpA and PFOA reached 2.2 ppt at the highest result. The federal limits of 4.0 ppt for PFOA and PFOS have a 2029 compliance date, and in May 2026 the EPA proposed extending it to April 26, 2031.
Conductivity matters for heaters: A.O. Smith says anode rod wear depends on how well water conducts electricity, so a pitted rod should be checked more often.
EWG's view
The Environmental Working Group, an advocacy group, has a Monterey Park Water Department page using 2014 to 2023 data. It flags 14 of 28 detected contaminants as above its guidelines, many of which are California's health goals. For example, it lists arsenic at 1.18 ppb against a 0.004 ppb guideline, and chromium-6 at 2.80 ppb against 0.02 ppb. Treat EWG as a stricter yardstick on older data, not as new tests of today's water. EWG shows no legal limit for chromium-6, while the city's report lists a state limit of 10 ppb. EWG's haloacetic acid figure (34.9 ppb) does not match the city's (2.15 ppb), so we left it out.
Treatment advice
The EPA calls water above 120 mg/L hard and says softeners are often recommended above 180 mg/L. It also says carbon filters do not remove nitrates and no single system removes all contaminants. Chloramine, which this report does not list, is the disinfectant a Stanford utilities memo ties to rubber parts wearing out early.
Cited sources
- City of Monterey Park, 2025 Water Quality Report (CCR, 2025 data)
- City of Monterey Park, Water Quality Report page
- Environmental Working Group, Tap Water Database, Monterey Park Water Department
- U.S. EPA WaterSense, Guide to Selecting Water Treatment Systems (PDF)
- U.S. EPA WaterSense, Soften Water Without Wasting It (PDF)
- A.O. Smith, To remove water scale from tank type glass-lined water heaters, Form 4800 (PDF)
- U.S. Geological Survey, Hardness of water
- Stanford Utilities, chloramine and rubber components (quoting the CA-NV AWWA complaints handbook)
- Golden State Water, South San Gabriel 2025 Consumer Confidence Report
- Federal Register, Extending the Compliance Deadline for the PFOA and PFOS Maximum Contaminant Levels (proposed, May 20, 2026)