Norwalk has five wells and uses none of them. Here is where the water actually comes from, what Norwalk's own 2025 test results say, and what an under-sink system changes.
Norwalk sits in Warren County with its own utility department and its own water tower. It does not make its own water.
The Norwalk Water Supply system (public water supply ID 9164078, serving 14,334 people) holds five groundwater wells, Norwalk #1 through #5, drilled between 1949 and 1961. The Iowa DNR lists every one of them at status "Not Used." The same DNR record classifies Norwalk's source water type as "Purchased Surface Water." Norwalk appears on Des Moines Water Works' published list of wholesale customers, and it is one of the twelve founding members of Central Iowa Water Works, the regional production authority established in 2024. So the water in a Norwalk kitchen faucet is treated river water that arrives through a transmission main from the north, not groundwater pulled from under Warren County.
Des Moines Water Works operates three treatment plants for Central Iowa Water Works, drawing from the Raccoon River and the Des Moines River. In the utility's own words, those two rivers are what make drinking water for 600,000 central Iowans. Norwalk is one of roughly twenty communities buying finished water off that system.
DMWW names the communities served by its L.D. McMullen plant, and Norwalk is not on that list. The Fleur Drive plant is described as serving "all other DMWW-area customers," which by elimination would include Norwalk, but no public document we could find says so by name. We would rather tell you that than pretend to a detail we cannot source.
This matters for one practical reason. Surface water carries far more organic material than groundwater does, and organic material plus chlorine is exactly how trihalomethanes get made. Norwalk's water chemistry is a downstream consequence of being a purchased-surface-water city. Which brings us to Norwalk's own numbers.
Every number below comes from Norwalk's own row in the 2026 Drinking Water Quality Report covering the 2025 data year, published jointly by Central Iowa Water Works and Des Moines Water Works and linked from the City of Norwalk utility page.
µg/L average trihalomethanes in Norwalk's distribution system against a federal limit of 80, the highest average of any system listed in the report.
2026 Water Quality Report ↗µg/L highest single trihalomethane sample taken in Norwalk during 2025. The federal maximum contaminant level is 80.
2026 Water Quality Report ↗Norwalk wells currently in service. All five are listed by the Iowa DNR at status "Not Used," so 100% of the city's water is purchased.
Iowa DNR source water record ↗| Norwalk distribution system, 2025 | Result | Range | Limit |
|---|---|---|---|
| Total trihalomethanes (TTHM) | 76 µg/L | 60 to 110 | 80 µg/L |
| Haloacetic acids (HAA5) | 12 µg/L | 7 to 18 | 60 µg/L |
| Free chlorine (annual average) | 1.00 mg/L | 0.42 to 1.51 | 4 mg/L |
| Lead, 90th percentile | Non-detect | ND to 15 µg/L | 15 µg/L action level |
| Coliform bacteria | 0 positive | 10 monthly samples | Presence / absence |
| Trihalomethanes across the regional system, 2025 | Annual average | Highest single sample |
|---|---|---|
| Norwalk | 76 µg/L | 110 µg/L |
| Urbandale | 70 µg/L | 99 µg/L |
| Waukee | 61 µg/L | 92 µg/L |
| Clive | 60 µg/L | 77 µg/L |
| Des Moines | 56 µg/L | 77 µg/L |
| Warren Water District | 50 µg/L | 63 µg/L |
| Ankeny | 49 µg/L | 66 µg/L |
| Johnston | 36 µg/L | 55 µg/L |
Norwalk's water met every federal standard in 2025. We are not going to tell you otherwise, and anyone who does is selling you something. The trihalomethane rule is written against a running annual average, and Norwalk's average was 76 against a limit of 80. Under the limit is under the limit. No violation was issued.
Here is what is still worth knowing. Norwalk posted the highest trihalomethane average of any distribution system printed in that report, and one Norwalk sample came back at 110 µg/L. No other system in the report produced a reading that high. Urbandale's peak was 99, Waukee's was 92, and Des Moines and Clive both topped out at 77. An average of 76 with a spread running from 60 all the way to 110 means the number moves a lot depending on where in Norwalk the sample was drawn and when.
Trihalomethanes are not added to the water on purpose. They form after treatment, when free chlorine keeps reacting with organic matter as the water sits in pipes and storage. Longer travel time generally means more of them, which is a plausible reason a purchased-water city at the end of a long main reads higher than the city producing the water. That is the general chemistry, not a documented finding about Norwalk's specific pipe network, and we will flag the difference. The EPA regulates this group because researchers have connected long-term exposure to disinfection byproducts with elevated cancer risk, and Iowa has the second-highest cancer incidence rate in the country. That is a fact worth sitting with. It is not a claim that Norwalk's tap water caused anyone's illness, and we will not make that claim. Investigate Midwest, Mar 2026 ↗
The rest of Norwalk's row is genuinely good news, and it deserves saying out loud. HAA5 at 12 µg/L is a fifth of the limit. Ten coliform samples through the year, zero positives, which is a cleaner bacteriological record than Des Moines, Urbandale or East Dallas Water managed in the same report. The lead 90th percentile was non-detect, meaning most sampled Norwalk homes returned no measurable lead at all. The reported range does reach the 15 µg/L action level at the top end, which is the signature of one house's own plumbing rather than a system-wide problem.
One more Norwalk-specific detail: the disinfectant here is free chlorine, not chloramine, at a 1.00 mg/L annual average with a range of 0.42 to 1.51. Chloramine shows up in some fringe metro systems such as Bondurant and Xenia Rural Water. That distinction matters when you are comparing filters, because the two behave very differently in carbon.
Central Iowa Water Works listed Norwalk by name in its Stage III announcements in 2025 and again in 2026.
The first Stage III ban in the region's history. All residential and commercial lawn watering stopped, Norwalk included. Nitrate hit 14.39 mg/L in the Raccoon River and 14.04 mg/L in the Des Moines River the day it was issued, against a 10 mg/L drinking water limit.
CIWW Stage III updates ↗It happened again on June 8. CIWW stated the regional system was "operating at the limits of its available treatment resources." The Water Works Park infiltration gallery reached 12.3 mg/L and stayed above 10 for roughly 90 days, a record. Restrictions eased back to Stage II for all customers on July 20, 2026.
CIWW Stage III warning ↗Those bans were never about running out of water. They were about protecting the utility's ability to strip nitrate out fast enough to stay under the legal limit, and cutting outdoor demand lets the nitrate removal system keep pace. In 2025 the treated water leaving the Fleur Drive plant peaked at 9.17 mg/L nitrate and McMullen at 9.04, both under the 10 mg/L standard but with very little room left. Researchers have linked long-term nitrate exposure in drinking water to several cancers. Norwalk has no local buffer against any of this. A city with its own working wells has options when a river goes bad. With all five Norwalk wells sitting at "Not Used," the city's supply moves with whatever the Raccoon River is doing that week.
Norwalk counted 12,799 residents in the 2020 census. The city paid for its own special census in 2024 and came back with 14,334, a 12% jump in four years. That same 14,334 is the population-served figure the Iowa DNR carries for the Norwalk water system, so the two records line up exactly.
The city's own neighborhoods page reads like a build schedule: Lakewood at roughly 600 homes around Lake Colchester and still expanding, The Legacy with 900-plus residences around an 18-hole golf community, and the Timber View, Timber Ridge, Silverado and Blooming Heights cluster on the west side at about 450 homes. New kitchens almost always mean granite or quartz, which is why we drill natural stone in house instead of sending you to a countertop shop.
Norwalk is not all new. The Founder's District and Norwalk Knolls make up the original townsite, described by the city as home to some of Norwalk's oldest houses, and Echo Valley has been going up around Echo Valley Country Club since the early 1970s. In homes that age, interior plumbing and fixtures are the realistic lead source, which is exactly what a lead range topping out at 15 µg/L in an otherwise non-detect city reflects.
The two things showing up in Norwalk's report, trihalomethanes in the pipes and nitrate pressure upstream, are both handled at the tap rather than at the plant.
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