Tap water report · updated November 2026
San Jose tap water: hard water, PFOS samples up to 6.2 ppt (EPA limit 4)
What’s in the water San Jose Water delivers to 1 million people, from national testing by the U.S. Environmental Protection Agency (EPA) and the utility’s own report.
Short answer
San Jose tap water is hard: about 8.8 grains per gallon (151 milligrams per liter (mg/L)), depending on which treatment plant serves your neighborhood (99 to 288 mg/L), according to published water quality data from San Jose Water (2025). The U.S. Environmental Protection Agency’s (EPA’s) 2023–25 testing found PFOS (a PFAS “forever chemical”) at 6.2 parts per trillion (ppt) in its highest samples, above the 4 ppt limit utilities must meet by 2029. The system had 1 health-based violation in the five years through September 2026, since resolved.
Sources: San Jose Water 2025 data, EPA UCMR 5, EPA SDWIS 2026Q3 · Sources and method
How San Jose compares with the 40 systems we track
Hardness
10th hardest
of 34 systems
PFOA / PFOS
8th highest
of 11 that detected any
Lithium
14th highest
of 14 that detected it
Size
20th largest
of 40 by people served
01 · What it means
What these readings mean for your home
Each reading in plain English: what it is, how San Jose compares with the other systems we track, and whether there’s anything to do. The tags follow EPA’s limits and reference levels where EPA has one; for hardness, which has no EPA limit, they follow the U.S. Geological Survey (USGS) scale and Minnesota’s health department. New to the acronyms? Every term, in plain English.
Hardness
Worth acting onHardness is dissolved calcium and magnesium, picked up as water runs through rock. It isn’t a health issue (EPA has no limit for it). It’s what leaves white crust on faucets, spots on glasses and scale inside your water heater. It’s measured in grains per gallon (gpg); 1 gpg is about 17 mg of minerals in a liter.
Here: At 8.8 gpg, San Jose water is hard, the 10th-hardest of the 34 systems we track. Most homes here notice scale and spotting.
What to do: A water softener is the only whole-house system that removes hardness. Size it to your household so it doesn’t waste salt.
What the research says: Studies tie hard water to more soap use and scale. Observational studies link it with somewhat more eczema in babies, but in the largest trial a softener didn’t improve existing eczema. The studies →
Learn more →PFAS (PFOA and PFOS)
Worth acting onPFAS are a family of thousands of manufactured chemicals used in many consumer and industrial products. They break down very slowly, which is why people call them "forever chemicals." PFOA and PFOS are the two EPA regulates most tightly. They’re measured in parts per trillion (ppt): 1 ppt is about one drop in 20 Olympic swimming pools.
Here: San Jose’s highest PFOS sample was 6.2 ppt, about 1.6 times EPA’s 4 ppt limit, the 8th-highest of the 40 we track. 11 of the 40 had a sample over the limit; 29 had none detected at all. These are samples from EPA’s 2023–25 testing, not a violation: utilities have until 2029 to get under the limit on a yearly average.
What to do: A filter on the tap you drink and cook from handles it. Look for reverse osmosis certified to NSF/ANSI 58, or carbon certified to NSF/ANSI 53, for PFOA and PFOS by name.
What the research says: EPA and the National Academies link PFOA and PFOS exposure to higher cholesterol, lower vaccine response, lower birth weight and some cancers, mostly over years of drinking the water. The studies →
Learn more →Disinfectant
Nothing to doUtilities add a small amount of chlorine, or chloramine (chlorine combined with a little ammonia), so germs can’t grow in the pipes on the way to your tap. EPA allows up to 4 milligrams per liter (mg/L) of either and says water within its standards can be used for drinking, cooking and bathing.
Here: San Jose uses chloramine in part of its system, like 20 other systems we track. It lasts longer in pipes than chlorine and is harder to filter.
What to do: For taste, use catalytic carbon or a filter certified to NSF/ANSI 42 for chloramine. Fish tanks and home dialysis need it removed completely.
What the research says: Health agencies call these levels acceptable for drinking and bathing; dialysis and fish tanks are the exceptions. Studies haven’t shown shower chlorine harms skin or hair. The studies →
Learn more →Lithium
Nothing to doLithium is a metal that occurs naturally in some rock and groundwater. There’s no legal limit in drinking water. EPA screens results against 10 micrograms per liter (µg/L) while it studies whether a limit is needed.
Here: San Jose’s highest sample was 10.0 µg/L. EPA compares results to one significant digit, so that rounds to its 10 µg/L screening level and doesn’t count as above it.
What to do: Nothing to do.
What the research says: Some regional studies link natural lithium with lower suicide rates and the largest individual study found no link. EPA’s screening level is cautious, not a harm threshold. The studies →
Learn more →Health-based violations
Worth knowingA health-based violation means the utility broke a federal drinking water rule tied to health: it went over a limit, or skipped a required treatment step. Missing a paperwork deadline doesn’t count.
Here: San Jose’s system had 1 in the five years through September 2026, all since resolved. 36 of the 40 systems we track had none.
What to do: Utilities must notify customers when a violation happens. The utility’s annual water quality report explains what happened and what was fixed.
Learn more →How San Jose compares: highest PFOA or PFOS sample
Parts per trillion (ppt), from EPA’s 2023–25 testing. The dashed line is EPA’s limit of 4.
- Miami33.0 PFOS
- El Paso8.5 PFOS
- Fort Worth8.3 PFOA
- Philadelphia8.1 PFOA
- Louisville7.5 PFOA
- Tampa6.9 PFOS
- Dallas6.3 PFOA
- San Jose6.2 PFOS
- Cincinnati6.1 PFOS
- Columbus5.3 PFOA
- Austin4.8 PFOS
If you live in San Jose
- Size a softener for San Jose water At 8.8 grains per gallon, the calculator works out the capacity for your household.
- What softeners cost Store and dealer prices, with what each includes.
- Drinking water filters listed for PFOA and PFOS Under-sink systems with a public NSF, WQA or IAPMO listing, and what they cost.
- Whole-house filters for chloramine San Jose uses chloramine, which ordinary carbon removes slowly. What to look for and what it costs.
San Jose’s water is hard. Softeners from brands that sell online, at their own store prices:
We may earn a commission from these links.
02 · The full results
Every PFAS result EPA recorded
In EPA’s national testing (sampled 2023 to 2025), San Jose’s highest samples reached PFOS at 6.2 ppt, above EPA’s 4 ppt limit. These are individual samples, not a compliance finding: water systems have until 2029 to meet the limit, judged on a yearly average.
Lithium peaked at 10.0 µg/L, which rounds to EPA’s 10 µg/L health reference level and doesn’t count as above it under EPA’s method.
Results from EPA’s national testing program (UCMR 5) for San Jose Water, 19 sampling points, February 2023 to February 2025. Concentrations in parts per trillion (ppt).
| Chemical | Samples | Detected | Highest | EPA limit |
|---|---|---|---|---|
| PFOA (perfluorooctanoic acid) | 37 | 0 | none | 4 |
| PFOS (perfluorooctane sulfonic acid) | 37 | 2 | 6.2 | 4 |
| PFHxS | 36 | 12 | 5.5 | 10 |
| PFNA | 37 | 0 | none | 10 |
| HFPO-DA (GenX) | 37 | 0 | none | 10 |
"None" means every sample was under EPA’s reporting level (4 ppt for PFOA). PFHxS, PFNA and HFPO-DA (GenX) are three other PFAS chemicals; EPA proposed removing their limits in May 2026, and that isn’t final.
03 · Where it comes from
The source, and who else drinks it
SJW delivers groundwater from its wells, local mountain surface water from the Santa Cruz Mountains, and imported surface water bought from Valley Water, and its service area map shows which source primarily serves each area.
San Jose Water serves about 1 million people directly, and 18 other water systems buy water from it, serving about 131,927 more. If you live in one of them, most of what’s on this page describes your water too, though hardness and disinfectant can change if your system blends in its own wells.
SJW’s groundwater is its hardest source, averaging 288 parts per million (ppm), compared with 99 ppm for the treated surface water it buys from Valley Water.
EPA’s federal database shows 1 health-based violation in the five years through September 2026. The system missed a required treatment step under EPA’s rules for treating river and lake water in June 2023, since resolved.
Largest systems that buy from San Jose Water
- Great Oaks Wc INC112,582
- City of Cupertino16,336
- Summit West Mutual Water Co.481
- Villa Del Monte Mwc422
- Chemeketa Park Mutual Water Company346
- Mt. Pleasant Water Users Association300
- Saratoga Heights Mutual Water Company258
- Ridge Mutual Water Company213
- Big Redwood Park Water182
- Mt. Eden Mutual Water Company165
From EPA’s federal drinking water database (SDWIS), 2026Q3: community systems with an active connection buying from CA4310011. Population served.
ZIP codes San Jose Water reports serving (30)
95008 · 95014 · 95030 · 95032 · 95033 · 95050 · 95070 · 95110 · 95111 · 95112 · 95113 · 95116 · 95117 · 95118 · 95120 · 95121 · 95122 · 95123 · 95124 · 95125 · 95126 · 95127 · 95128 · 95129 · 95130 · 95131 · 95132 · 95133 · 95136 · 95148
From EPA’s UCMR 5 ZIP file. A ZIP can be served by more than one system; your water bill names yours. Look up any ZIP.
04 · Questions
San Jose water questions
Is San Jose tap water safe to drink?
The U.S. Environmental Protection Agency (EPA) doesn’t grade a city’s tap water as safe or unsafe; it sets limits and records violations. By that record, San Jose’s water system had 1 health-based violation in the five years through September 2026, all since resolved. Separately, EPA’s 2023–25 testing found PFOA or PFOS (two PFAS “forever chemicals”) samples above the 4 parts per trillion (ppt) limit that utilities must meet, on a yearly average, by 2029. A filter certified to NSF/ANSI 53 or 58 for PFOA and PFOS addresses it at the tap.
Is San Jose tap water hard?
San Jose tap water is hard: about 8.8 grains per gallon (151 milligrams per liter (mg/L)), depending on which treatment plant serves your neighborhood (99 to 288 mg/L), according to published water quality data from San Jose Water (2025).
Does San Jose tap water have PFAS?
In the U.S. Environmental Protection Agency’s (EPA’s) national testing (sampled 2023 to 2025), San Jose’s highest samples reached PFOS (a PFAS “forever chemical”) at 6.2 parts per trillion (ppt), above EPA’s 4 ppt limit. These are individual samples, not a compliance finding: water systems have until 2029 to meet the limit, judged on a yearly average.
Does San Jose use chlorine or chloramine?
Chlorine and chloramine. San Jose Water (SJW) states that chloramine and chlorine may be present in the water it provides, and the report does not say which areas receive which.
Has San Jose’s water system had violations?
The U.S. Environmental Protection Agency’s (EPA’s) federal database shows 1 health-based violation in the five years through September 2026. The system missed a required treatment step under EPA’s rules for treating river and lake water in June 2023, since resolved.
Is there lithium in San Jose water?
Lithium peaked at 10.0 micrograms per liter (µg/L), which rounds to the U.S. Environmental Protection Agency’s (EPA’s) 10 µg/L health reference level and doesn’t count as above it under EPA’s method.
Nearest cities we cover
Sources
- 01San Jose Water, 2025 water quality data (hardness), read 2026-11-04
- 02San Jose Water (source water)
- 03San Jose Water (disinfectant)
- 04EPA, Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) occurrence data, file posted 2026-10-15
- 05EPA, Safe Drinking Water Information System via ECHO, 2026Q3 file
- 06EPA, PFAS National Primary Drinking Water Regulation, 89 FR 32532
- 07EPA UCMR 5 Data Summary (July 2026)
- 08USGS Water Science School, "Hardness of Water"
EPA system ID CA4310011 · San Jose Water