Hardness
Very Hard
450 PPM · 26.3 GPG
Local water dashboard
Official source aggregationWater quality in San Luis, AZ 85349
A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for Yuma County.
1 active health-based violation
- Primary matched system
- San Luis City Of
- Source water
- Groundwater
- County
- Yuma County
- Profile updated
At a glance
What the current records say
EPA quarter 2026Q2
Compliance screen
Review needed
1 active health-based record
Lead 90th percentile
0.001 mg/L
7% of action level
Utility match
1 system
Serves 39,705 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
450 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
450
mg/L as CaCO₃ equivalent
Grains per gallon
26.3
1 GPG ≈ 17.1 PPM
What this means at home
At 450 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
101
Nearest site
17.4 mi
Observation range
Mar 8, 2016–Apr 9, 2026
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: 016S021E36B006S (Well).USGS source documentation ↗
Regional context
Is 85349 typical?
These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.
San Luis median
449 PPM
About the same3 indexed ZIP readings · Range 402–450 PPM
Arizona median
241 PPM
209 PPM higher285 indexed ZIP readings · Range 66.4–1250 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 pass
Lead (PB90)
0.001 mg/L
Reported Dec 31, 2024
Copper (CU90)
Not available
No numerical 90th-percentile result
Numerical coverage
1 comparable result
Missing values remain blank; absence is not treated as a pass.
Lead (90th percentile)
Measured in mg/L
Local 0.001
EPA limit 0.015
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 9
- Health-based
- 3
- Active health-based
- 1
| Contaminant or rule | System | Status | Period |
|---|---|---|---|
| Lead and Copper Rule | AZ0414005 | Resolved | Oct 1, 2024through Nov 1, 2024 |
| Groundwater RuleHealth-based | AZ0414005 | Resolved | Jun 6, 2024through Dec 30, 2024 |
| Revised Total Coliform Rule | AZ0414005 | Resolved | Feb 1, 2024through Mar 19, 2024 |
| Lead and Copper Rule | AZ0414005 | Resolved | Sep 28, 2021through Jan 31, 2022 |
| Revised Total Coliform RuleHealth-based | AZ0414005 | Unaddressed | Sep 15, 2021 |
| TTHM | AZ0414005 | Resolved | Sep 8, 2021through Mar 7, 2022 |
| E. COLI | AZ0414005 | Resolved | Sep 1, 2021through Jul 5, 2022 |
| Groundwater RuleHealth-based | AZ0414005 | Resolved | Aug 5, 2021through Nov 12, 2021 |
| Revised Total Coliform Rule | AZ0414005 | Resolved | Aug 1, 2021through Oct 28, 2021 |
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 San Luis ZIP 85349 using 450 PPM nearby hardness and 1 reported measurement benchmarks.
Scale protection
High-Capacity Whole House Water Softener
450 PPM is 4× 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
Revised Total Coliform Rule 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 San Luis
Estimates can differ across a city because monitoring locations and associated systems differ.
Frequently asked
Water questions for San Luis
Is tap water safe in San Luis?+
EPA ECHO reports 1 active health-based violation among the associated community water systems. Review the affected utility's current notice and Consumer Confidence Report.
How hard is the water?+
Nearby USGS observations produce an estimate of 450 PPM, or 26.3 grains per gallon, classified as very hard. This is not a household tap measurement.
Do I need a water softener?+
At 450 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.