Is San Jose tap water safe to drink?

Parts of San Jose receive chloramine and parts receive free chlorine, according to its own water quality reporting. Which one reaches your tap depends on the zone or source that serves your address; the utility's service map or customer line can tell you.

If you are unsure, choose filters rated for chloramine. They handle free chlorine too.

San Jose's water measures about 10.8 grains per gallon (185 mg/L as calcium carbonate), which is very hard on the US Geological Survey scale: soft below 60 mg/L, moderately hard 60-120, hard 120-180, very hard above 180.

Hard water is not a health risk, but it is expensive. It leaves scale in water heaters, dishwashers and fixtures, spots glassware, and makes soap lather poorly. Only an ion-exchange softener removes the minerals. Filters, including shower filters, do not soften water, whatever the packaging implies. A salt-free scale conditioner reduces scale buildup without removing minerals, and needs no drain line.

Hardness data: TapWaterData Water Hardness Dataset (tapwaterdata.com), licensed CC BY 4.0. Underlying source: Utility-reported water quality data — SAN JOSE WATER (PWSID CA4310011), 2025-10-07.

In San Jose Water's most recent lead sampling, for the period ending December 2025, 90% of tested homes came in at or below 0 ppb of lead. That means at least 90% of sampled homes had no measurable lead.

This is a system-wide statistic, not a reading of your tap. Lead comes from lead service lines, old solder and some brass fixtures inside homes, so two houses on the same street can differ. Testing your own tap costs $15-40, and many utilities test free on request.

EPA's lead action level is 15 parts per billion (ppb) today and drops to 10 ppb in November 2027 under the Lead and Copper Rule Improvements. FDA's limit for bottled water is 5 ppb. EPA's health goal for lead is zero.

In EPA's 2023-2025 sampling of San Jose Water, these PFAS were detected: PFOS up to 6.2 ppt (2024 limit 4); PFHxS up to 5.5 ppt (2024 limit 10). PFOS was measured above the 2024 limit in at least one sample. These are the highest single results; utilities are judged on running annual averages, so a high sample is not by itself a violation.

Reverse osmosis is the most reliable home treatment for PFAS. Some carbon filters are certified for PFOA and PFOS reduction under NSF/ANSI 53; check the product listing for that claim, not just the word PFAS on the box.

In April 2024 EPA set enforceable limits of 4 parts per trillion (ppt) for PFOA and PFOS, and 10 ppt for PFHxS, PFNA and HFPO-DA (GenX). In May 2025 EPA said it intends to keep the PFOA and PFOS limits, extend the compliance deadline to 2031, and rescind the other three. We compare results to the 2024 limits and label which ones may change.

EPA's records show 1 health-based violation for San Jose Water since 2016: Surface Water Treatment Rule (1). The most recent began in June 2023.

A violation records a period when a standard or treatment requirement was missed. It is not a description of today's water, and many are resolved within the quarter. The utility's annual report explains each one.

San Jose is in Santa Clara County, which EPA places in Radon Zone 2: the predicted average indoor level is between 2 and 4 pCi/L. (Large cities can span more than one county; we use the county at San Jose's geographic center.)

Zone describes a county average. Individual homes in every zone test high, so EPA recommends testing every home, especially basements and ground floors. Fix at 4 pCi/L or above.

EPA radon zones describe counties, not houses. Zone 1 counties have a predicted average indoor level above 4 picocuries per liter (pCi/L), Zone 2 between 2 and 4, Zone 3 below 2. Homes with high levels are found in every zone, which is why EPA recommends that every home be tested, and fixed at 4 pCi/L or above. See every California county's radon zone.