Here is what the EPA's own data shows about tap water in Rancho Cucamonga. According to EPA SDWIS data retrieved October 2026, Rancho Cucamonga is served by 7 active community water systems, together reported to serve about 1,553 people.
As of October 2026, EPA records show 15 violations across the community water system(s) serving Rancho Cucamonga, going back to the earliest EPA record. 2 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.
As of October 2026, EPA records show no reported violations for this system in the period covered. This is not a guarantee about every substance, or about the water inside your home's plumbing.
Californian Mobile Home Park
372 served · groundwater · PWSID CA1900843
Health-based Heterotrophic Bacteria (HPC or SPC): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in September 2019. 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: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 3 times between July 2017 and October 2021. All have since returned to compliance, per EPA records.
Monitoring COPPER, FREE: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2019. EPA records do not show all of these as returned to compliance.
Monitoring Lead: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2019. EPA records do not show all of these as returned to compliance.
Monitoring Nitrate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2017. 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 3 times between July 2016 and November 2016. All have since returned to compliance, per EPA records.
El Rancho Mobile Home Park
215 served · groundwater · PWSID CA1900636
As of October 2026, EPA records show no reported violations for this system in the period covered. This is not a guarantee about every substance, or about the water inside your home's plumbing.
Desert Palms Mobile Home Park
140 served · groundwater · PWSID CA1900693
Monitoring Lead and Copper Rule: 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.
Terra Nova Mobile Home Park
140 served · groundwater · PWSID CA1900721
As of October 2026, EPA records show no reported violations for this system in the period covered. This is not a guarantee about every substance, or about the water inside your home's plumbing.
Clear Skies Mobile Home Park
131 served · groundwater · PWSID CA1900817
Health-based Coliform (Pre-TCR): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in May 2020. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
Monitoring Coliform (Pre-TCR): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in May 2017. All have since returned to compliance, per EPA records.
Mono Vista Ranch Mhp
105 served · groundwater · PWSID CA5500124
Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in April 2024. All have since returned to compliance, per EPA records.
Monitoring Nitrate: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in January 2024. 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 October 2026. Records cover the EPA's full reporting history for these systems. Verify at EPA ECHO.