NM / San Ysidro
NM · Tap water records
San Ysidro tap water, in plain English
Here is what the EPA's own data shows about tap water in San Ysidro. According to EPA SDWIS data retrieved June 2026, San Ysidro is served by 1 active community water system, together reported to serve about 166 people.
As of June 2026, EPA records show 189 violations across the community water system(s) serving San Ysidro, going back to the earliest EPA record. 102 of these are classified by the EPA as health-based (a contaminant recorded above the limit the EPA tracks); the rest are monitoring or reporting violations. Each is listed by system below, with its status.
What the EPA has on record, by system
San Ysidro Water Supply System
166 served · groundwater · PWSID NM3509723 - Health-based Groundwater Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 4 times between July 2017 and July 2025. The EPA record for these does not include a measured level. EPA records do not show all of these as returned to compliance.
- Health-based LEAD AND COPPER RULE REVISIONS: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in October 2024. The EPA record for these does not include a measured level. EPA records do not show all of these as returned to compliance.
- Health-based Fluoride: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 83 times between April 2014 and July 2024. The EPA record lists a level of 5.5 MG/L; the limit (MCL) is 4 MG/L. EPA records do not show all of these as returned to compliance.
- Health-based Arsenic: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 12 times between July 2022 and April 2023. The EPA record lists a level of 0.056 MG/L; the limit (MCL) is 0.01 MG/L. EPA records do not show all of these as returned to compliance.
- Health-based Stage 1 Disinfectants and Disinfection Byproducts Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 2 times in August 2012. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
- Monitoring LEAD AND COPPER RULE REVISIONS: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in October 2024. EPA records do not show all of these as returned to compliance.
- Monitoring TTHM: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 9 times between January 2020 and November 2023. EPA records do not show all of these as returned to compliance.
- Monitoring Total Haloacetic Acids (HAA5): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 10 times between October 2020 and November 2023. EPA records do not show all of these as returned to compliance.
- Monitoring Arsenic: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 24 times between January 2020 and October 2022. All have since returned to compliance, per EPA records.
- Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 11 times between July 2015 and May 2022. All have since returned to compliance, per EPA records.
- Monitoring Fluoride: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 6 times between July 2021 and January 2022. All have since returned to compliance, per EPA records.
- Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 13 times between October 1999 and October 2021. All have since returned to compliance, per EPA records.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 4 times between August 2020 and September 2020. All have since returned to compliance, per EPA records.
- Monitoring Chlorine: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times in July 2020. EPA records do not show all of these as returned to compliance.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 6 times between October 2005 and October 2015. All have since returned to compliance, per EPA records.
What this means
A health-based violation means a contaminant was recorded above the limit the EPA tracks for it. A monitoring or reporting violation means a required test or report was late or missed — not that a contaminant was measured above a limit. “Returned to compliance” means the EPA recorded the issue as resolved.
This page summarizes the EPA's own records and does not assess whether your water is safe to drink. For the most current details, you can verify every record directly with the EPA, and contact your water system with questions.
Source: U.S. EPA Envirofacts SDWIS, retrieved June 2026. Records cover the EPA's full reporting history for these systems. Verify at EPA ECHO.