IRWD water quality results for 2025
Chart legend Drinking water standards established by U.S. EPA and DDW set limits for substances that may affect consumer health or aesthetic qualities of drinking water. These charts show the following water quality standards: • Maximum Contaminant Level (MCL): Highest level of a contaminant that is allowed in drinking water. Primary MCLs are set as close to the PHGs (or MCLGs) as is economically and technologically feasible. • Maximum Residual Disinfectant Level (MRDL): The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants. • Secondary MCLs : Set to protect odor, taste and appearance of drinking water. • Primary Drinking Water Standard: MCLs for contaminants that affect health along with monitoring and reporting requirements and water treatment requirements. • Regulatory Action Level (AL): Concentration of contaminant, which, if exceeded, triggers treatment or requirements that a water system must follow. What is a water quality goal? U.S. EPA and DDW set voluntary water quality goals for some contaminants. Water quality goals are often set at such low levels that they are not achievable in practice and are not directly measurable. Nevertheless, these goals provide useful guide posts and direction for water management practices. The charts in this report include three types of water quality goals: • Maximum Contaminant Level Goal (MCLG): Level of a contaminant in drinking water below which there is no known or expected risk to health; set by U.S. EPA. • Maximum Residual Disinfectant Level Goal (MRDLG): Level of a drinking water disinfectant below which there is no known or expected risk to health; do not reflect the benefits of the use of disinfectants to control microbial contaminants. • Public Health Goal (PHG): Level of a contaminant in drinking water below which there is no known or expected risk to health; set by the California EPA. How are contaminants measured?
How to read this report This Water Quality Report lists results from drinking water quality assessments in 2025. Chart data includes the range of detection, the typical sources of contaminants for a variety of regulated elements and how they compare to water quality standards. To provide customers more insight, tables include secondary standards for aesthetic qualities of the water, such as hardness, pH, color, and corrosivity. The legend defines acronyms, explains water quality standards and goals, and outlines how substances are measured. Your water has been tested for many more chemicals than are listed in this report, including unregulated metals, pesticides and volatile organic compounds. If you don’t see something on the chart, don’t worry. That does not mean we didn’t test for it. Rather, if we test for a chemical and don’t find it — or if its concentration is too low to be distinguishable — we don’t list it. For example, we tested for mercury. We didn’t find it. So we didn’t list it.
• Parts per million (ppm) or milligrams per liter (mg/L) • Parts per billion (ppb) or micrograms per liter (μg/L) • Parts per trillion (ppt) or nanograms per liter (ng/L)
2025 IRWD distribution system water quality
MCL (MRDL/MRDLG)
Average amount
Range of detections
MCL violation?
Disinfection byproducts Total Trihalomethanes (ppb) Haloacetic Acids (five) (ppb) Chlorine residual (ppm)
Typical source of contaminant Byproducts of chlorine disinfection Byproducts of chlorine disinfection Disinfectant added for treatment
80 60
32.0 *** 13.0 ***
ND - 43.4 ND - 13.2 ND - 5.4
No No No No No No
(4.0 / 4)
1.8
Aesthetic quality Color (color units)
15*
<3 0.1 <1
ND - 5
Erosion of natural deposits Erosion of natural deposits Erosion of natural deposits
Turbidity (NTU)
5* 3*
ND - 14.2
Odor (threshold odor number)
ND - 4
Other Fluoride (mg/L)
2/0.8**
0.54
0.11 - 0.82
No
Erosion of natural deposits, water treatment
Twelve locations in the distribution system are tested quarterly for total trihalomethanes and haloacetic acids; 60 locations are tested monthly for color and odor, and weekly for chlorine residual and turbidity. MRDL = Maximum Residual Disinfectant Level; MRDLG = Maximum Residual Disinfectant Level Goal; ND = not detected *Contaminant is regulated by a secondary standard; **MCL/Optimum Level for our climate; *** Highest running annual average at any individual sample location Lead and copper action levels at residential taps Action Level (AL) Public Health Goal (PHG) 90th percentile value Sites exceeding AL / number of sites AL violation?
Typical source of contaminant
Copper (ppm)
1.3
0.3 0.2
0.2476
0/73 0/73
No No
Corrosion of household plumbing
Lead (ppb) Corrosion of household plumbing The most recent lead and copper at-the-tap samples were collected from 72 residences in 2025. Lead was detected in zero homes and copper was detected in 60 homes, but none of the samples for lead and copper exceeded the respective regulatory Action Level (AL). A regulatory Action Level is the concentration of a contaminant which, if exceeded in more than 10% of samples, triggers treatment or other requirements that a water system must follow. Unregulated chemicals requiring monitoring in the distribution system Chemical Notification level PHG (MCLG) Average local and imported Range of detections Most recent sampling date Lithium, Total (ppb) n/a n/a 23.6 11.7 - 42 2025 Perfluoropentanoic acid (PFPeA) (ppt) n/a n/a 1.9 ND - 3.8 2025 Perfluorobutanoic acid (PFBA) (ppt) n/a n/a 7.85 7.8 - 7.9 2025 Perfluorooctanoic Acid (PFOA) (ppt) 4.0 0.007 0.19 ND - 2.3 2024 *Contaminant is regulated by a secondary standard. 15 <5
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IRWD Water Quality Report 2026
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