San Diego County, California has about 3,298,799 residents (Census 2024 estimate) and 82 community water systems in EPA records. The largest local system is San Diego, City of, serving about 1,408,937 people from surface water.
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
San Diego, City of Measured (utility report, 2025) · High confidence
200–285 mg/L (varies by area; no single average published)
Source: SAN DIEGO, CITY OF water quality report, 2025
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
For a 3-person home using 57 gallons per person per day and regenerating weekly, you'd remove about 16,997 grains between regenerations. Suggested size: 24,000 grain. Hardness varies by area here, so this uses the harder plant's figure (14.2 gpg). If your address gets softer water, a smaller unit may do; check your area in the utility report or test your tap.
Estimate only. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
The 6 biggest of 82 community water systems on EPA records for this county. Service areas don't follow county lines; your water bill names your provider.
CA3710020 · serves about 1,408,937 people · Surface water
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2024-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
CA3710010 · serves about 277,918 people · Surface water
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2022-01-01) Older result. Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
CA3710034 · serves about 242,155 people · Surface water
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2024-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
CA3710025 · serves about 184,915 people · Surface water
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2021-01-01) Older result. Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
CA3710014 · serves about 174,340 people · Surface water
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2022-01-01) Older result. Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
CA3710006 · serves about 137,044 people · Surface water
Lead 90th percentile: 1.1 ppb (period starting 2022-01-01) Older result. Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
A PFAS detection is not a violation. Federal limits (4 ppt for PFOA and PFOS) apply to running annual averages, with compliance required by 2029. In May 2026 EPA proposed extending the PFOA/PFOS deadline to 2031 and removing other PFAS limits; not final as of 2026-10-21.
These are public records for whole systems. Your home's pipes, fixtures and any private well can change what you drink. A certified lab test or a hardness test strip gives you your own numbers. Then use our PFAS and lead filter selector to see which certifications to look for.
None of the 6 largest systems here have a health-based violation in EPA records since October 2021. San Diego, City of's most recent lead 90th percentile was below the lab detection limit (2024), below the 15 ppb action level. Public records can't guarantee what comes out of your tap, especially with older plumbing, so a home test is the surest check.
San Diego, City of reports hardness from 200 to 285 mg/L depending on where you live, with no single system-wide average, so check your area in its report or test your water. For a 3-person home at 14.2 gpg (the harder plant's figure, since your address may get either), our softener calculator suggests a 24,000 grain unit as a starting point.
1 of the 6 sampled systems listed here detected at least one PFAS in EPA's UCMR 5 testing, and 2 results were above the level of a federal limit in at least one sample. A detection isn't a violation: federal PFAS limits apply to running annual averages starting in 2029.
Most homes are served by San Diego, City of or one of the other systems listed on this page, but service areas don't follow county lines. Your water bill names your provider, and its annual Consumer Confidence Report has the full test results.
Data as of October 21, 2026. Figures are copied from public records and combined with our own calculations; they can be out of date or wrong. Tapped Out isn't affiliated with any utility or the EPA. Written and reviewed by the Tapped Out team. How we calculate · All sources.