Hardness
Very Hard
264.5 PPM · 15.5 GPG
Local water dashboard
Official source aggregationWater quality in Stockton, CA 95211
A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for San Joaquin County.
1 reported benchmark flag
- Primary matched system
- City Of Stockton
- Source water
- Surface water
- County
- San Joaquin County
- Profile updated
At a glance
What the current records say
EPA quarter 2026Q2
Compliance screen
No active flag
0 active health-based records
Lead 90th percentile
0 mg/L
0% of action level
Utility match
2 systems
Serves 191,302 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
264.5 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
264.5
mg/L as CaCO₃ equivalent
Grains per gallon
15.5
1 GPG ≈ 17.1 PPM
What this means at home
At 264.5 PPM, mineral scale can build up on fixtures and heating elements, reduce soap lather, and leave visible spotting. Hardness is primarily an aesthetic and appliance concern—not itself a tap-water safety rating.
USGS sites used
66
Nearest site
13.2 mi
Observation range
Jan 13, 2016–Jun 3, 2026
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: BACON ISLAND SOUTH POND NR ORWOOD CA (Lake, Reservoir, Impoundment).USGS source documentation ↗
Regional context
Is 95211 typical?
These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.
Stockton median
271 PPM
6 PPM lower11 indexed ZIP readings · Range 254–290 PPM
California median
189 PPM
76 PPM higher678 indexed ZIP readings · Range 3.3–728.5 PPM
EPA benchmark screen
Contaminant snapshot
Available numerical results from associated SDWIS community water systems, compared with the applicable action level or federal MCL. Federal measured-value coverage is incomplete.
1 pass1 fail
Lead (PB90)
0 mg/L
Reported Dec 31, 2026
Copper (CU90)
Not available
No numerical 90th-percentile result
Numerical coverage
2 comparable results
Missing values remain blank; absence is not treated as a pass.
Lead (90th percentile)
Measured in mg/L
Local 0
EPA limit 0.015
TTHM
Measured in MG/L
Local 0.083
EPA limit 0.08
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 7
- Health-based
- 5
- Active health-based
- 0
| Contaminant or rule | System | Status | Period |
|---|---|---|---|
| Nitrate | CA3910012 | Resolved | Jan 1, 2024through Dec 31, 2024 |
| TTHMHealth-basedReported 0.083 MG/L · MCL 0.08 | CA3910012 | Resolved | Apr 1, 2023through Jun 30, 2023 |
| TTHMHealth-basedReported 0.082 MG/L · MCL 0.08 | CA3910803 | Resolved | Apr 1, 2023through Jun 30, 2023 |
| TTHMHealth-basedReported 0.081 MG/L · MCL 0.08 | CA3910012 | Resolved | Jan 1, 2023through Mar 31, 2023 |
| TTHMHealth-basedReported 0.081 MG/L · MCL 0.08 | CA3910803 | Resolved | Jan 1, 2023through Mar 31, 2023 |
| TTHMHealth-basedReported 0.089 MG/L · MCL 0.08 | CA3910803 | Resolved | Oct 1, 2022through Dec 31, 2022 |
| Lead and Copper Rule | CA3910012 | Resolved | Oct 1, 2021through Jan 10, 2025 |
No reported violation does not prove that every contaminant was tested or absent; SDWIS measured values are incomplete and lag state records.
Solutions matcher
Your personalized water action plan
Matched to Stockton ZIP 95211 using 264.5 PPM nearby hardness and 2 reported measurement benchmarks.
Scale protection
High-Capacity Whole House Water Softener
264.5 PPM is 2× the high-hardness trigger used by this matcher.
Designed to reduce scale on fixtures, water heaters, glassware, and plumbing throughout the home.
Compare whole-house systemsDrinking water protection
Under-Sink Reverse Osmosis System
TTHM has a measured benchmark flag or active health-based SDWIS record in this profile.
A certified multi-stage RO system targets a broader range of dissolved contaminants at the kitchen tap.
Explore under-sink filtrationAffiliate disclosure: we may earn a commission from qualifying purchases, at no added cost to you. Product matching is educational and does not replace certified water testing.
Nearby indexed reports
Compare ZIPs in Stockton
Estimates can differ across a city because monitoring locations and associated systems differ.
Frequently asked
Water questions for Stockton
Is tap water safe in Stockton?+
EPA ECHO shows no active health-based violation for the associated systems in this reporting snapshot. This does not prove every contaminant is absent; federal records can lag and household plumbing can change tap conditions.
How hard is the water?+
Nearby USGS observations produce an estimate of 264.5 PPM, or 15.5 grains per gallon, classified as very hard. This is not a household tap measurement.
Do I need a water softener?+
At 264.5 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.