Indiana PFAS in Drinking Water: What the EPA's 2023 to 2025 Monitoring Data Shows for Indianapolis, Carmel, and Noblesville

Under the EPA's fifth Unregulated Contaminant Monitoring Rule, which ran from 2023 to 2025, 56 Indiana water utilities reported PFAS detections and 19 exceeded the federal Maximum Contaminant Level for PFOA or PFOS. The central Indiana utilities serving Indianapolis, Carmel, and Noblesville all came in below the MCL. Here is what the data shows, how the monitoring worked, and what it means for households in Aqua Otter's service area.

How we compiled this data

The numbers in this article come from a single public source: the EPA's UCMR5 occurrence dataset, which the agency publishes and updates as utilities report results. We accessed the central Indiana results through WaterUtilityReport.com, which retrieves and indexes EPA's occurrence file by utility, and through Mapscaping.com's statewide analysis of the same federal dataset (both sources cited inline below). No proprietary data or internal Aqua Otter records were used. All PFAS values are in nanograms per liter (ng/L), which are equal to parts per trillion (ppt).

UCMR5 ran from 2023 through 2025. The EPA required all large water systems (serving over 10,000 people) plus a representative sample of small systems to test for 29 PFAS compounds and lithium. Results were submitted to EPA's national Safe Drinking Water Information System and released in rolling batches. The data referenced here was last retrieved on April 20, 2026, per the source metadata on WaterUtilityReport.com.

Central Indiana PFAS results: the dataset

Three utilities serve the bulk of Aqua Otter's Indianapolis metro customer base. Here is how each performed under UCMR5, according to EPA occurrence data retrieved via WaterUtilityReport.com (Citizens Water, Carmel Water, Indiana American Water Noblesville):

Source: EPA UCMR5 occurrence data via WaterUtilityReport.com, retrieved April 20, 2026. MRL = minimum reporting level. MCL = Maximum Contaminant Level. MCL values per EPA April 2024 PFAS NPDWR: 4 ng/L for PFOA and PFOS individually.

What the Indianapolis detections actually were

Citizens Water's 25 detections above the minimum reporting level did not include PFOA or PFOS, the two compounds with the 4 ppt MCL. One documented detection was PFBS (Perfluorobutane sulfonic acid) at 3.8 ppt, recorded at sampling point EP008 on July 12, 2024. PFBS does not have its own individual MCL. Instead, it contributes to the EPA's Hazard Index calculation alongside PFNA, PFHxS, and HFPO-DA. The Hazard Index MCL is 1.0 as a unitless sum of compound ratios. Citizens Water's reported Hazard Index value was below this threshold.

The remaining detections at Citizens Water were trace readings at or near the instrument detection limit for precursor compounds, short-chain PFAS, and fluorotelomer sulfonates. They were above zero but below the level where the EPA has set individual health standards. The EPA's dataset distinguishes between "official detection" (above MRL) and "official non-detect" (at or below MRL), and does not interpret either as a compliance determination. Utilities have until 2029 to comply with the new MCLs.

How Indiana compares statewide

The central Indiana picture is more favorable than the statewide average. According to Mapscaping.com's analysis of the EPA UCMR5 dataset (Indiana PFAS Map, April 2026):

• 56 Indiana water utilities detected at least one PFAS compound above the minimum reporting level.
• 19 utilities exceeded the final EPA MCL for PFOA or PFOS.
• Approximately 447,757 Indiana residents are served by utilities above the MCL.
• Approximately 2,148,985 Indiana residents are served by utilities with any PFAS detection above MRL.

The hardest-hit utilities are concentrated in areas with industrial history, proximity to military training sites that used AFFF (aqueous film-forming foam), or surface water sources affected by upstream manufacturing. The most extreme case in the state is Dyer Water Department in Lake County, which reported 78.3 ng/L of PFOS, 19.6 times the federal MCL, according to Mapscaping.com's analysis. Dyer is in northwestern Indiana near the Chicago metro industrial corridor.

Source: Mapscaping.com analysis of EPA UCMR5 occurrence data, published April 2026. Values reflect highest single sample per utility. Federal MCL of 4 ng/L for PFOA and PFOS finalized April 2024 (EPA PFAS NPDWR).

What the EPA's 2024 rule means and when it applies

The EPA published the first-ever national PFAS drinking water rule in the Federal Register on April 26, 2024 (89 FR 32532). The rule establishes enforceable MCLs for six PFAS compounds. PFOA and PFOS each get a 4 ng/L individual limit. PFNA, PFHxS, and HFPO-DA each get a 10 ng/L individual limit. A Hazard Index MCL of 1.0 applies to mixtures containing two or more of PFNA, PFHxS, HFPO-DA, and PFBS.

Water systems have until April 2029 to come into compliance. That five-year runway exists because treatment upgrades for PFAS, primarily granular activated carbon filtration, ion exchange resin, or high-pressure membrane systems, require significant infrastructure investment. The EPA has estimated that the rule will affect roughly 6,700 public water systems nationwide and cost roughly $1.5 billion per year industrywide once fully in place.

For the 19 Indiana utilities currently above the MCL, 2029 is the hard compliance deadline. For utilities like Citizens Water in Indianapolis, which detected PFAS but below the MCL, the rule creates ongoing monitoring obligations but no required treatment upgrade as of current readings.

What this means for homeowners in Indianapolis, Carmel, and Noblesville

The UCMR5 data gives central Indiana households a meaningful baseline. The utilities serving the Indianapolis metro tested their water, published the results, and came in below the federal threshold for the most regulated PFAS compounds. That is a materially different situation from the 19 utilities statewide that did not.

However, "below the MCL" does not mean "zero PFAS." Citizens Water had 25 compound-by-compound detections above the instrument minimum. The EPA's MCLs are health-risk thresholds calibrated against lifetime exposure, not indicators of whether a compound is present. Some households, particularly those with pregnant household members, infants, or people with compromised immune systems, choose to add a point-of-use reverse osmosis system as an additional layer regardless of whether their utility is in compliance.

An under-sink RO system removes PFAS from drinking and cooking water to levels below detection, per NSF/ANSI 58 testing. It does not address water used for bathing or laundry, which may matter for some populations, but for the vast majority of households the drinking and cooking water at the kitchen tap is the relevant exposure pathway. The Aqua Otter RO systems page covers how the process works and what system sizes make sense for a typical household.

Private wells are a different story

UCMR5 only covers public water systems. Private wells are not regulated under the Safe Drinking Water Act and are not part of the UCMR5 dataset. In Indiana, roughly 740,000 residents depend on private wells for drinking water, according to the Indiana Department of Health. Private wells in counties near industrial sites, agricultural land where PFAS-containing biosolids were applied, or former military bases with AFFF use history can carry PFAS at any concentration, with no monitoring requirement and no utility to be held accountable.

If your home in the Aqua Otter service area is on a well, PFAS is one of the things we test for in our in-home water analysis. Our full test includes PFAS, hardness, iron, manganese, pH, TDS, and coliform. For well water in Hamilton County and the broader Noblesville and Carmel periphery, the risk profile is not necessarily the same as the municipal picture above. Well testing gives you your specific, verifiable numbers. The well water testing guide covers what to look for and how to interpret results.

How to read your own utility's UCMR5 results

You do not need to parse the EPA's raw CSV file. Two publicly accessible tools let you look up your water system by name or ZIP code. WaterUtilityReport.com allows lookup by utility PWSID or city name and displays the UCMR5 record table in readable format. Mapscaping.com's Indiana PFAS Map plots every reporting utility on an interactive map with color coding by MCL status.

Your utility's PWSID is also on your annual Consumer Confidence Report (sometimes called the Water Quality Report or Drinking Water Report). Citizens Energy publishes its report at info.citizensenergygroup.com/water/quality/reports. Carmel Water and Indiana American Water publish equivalent reports. CCR reports are required to be mailed or made available to all customers annually and now include PFAS language as of the 2024 rule.

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