Katie Turpin turned on a light in the basement of her home in Des Moines to illuminate several cylinders attached to the wall.
Like other point-of-use reverse osmosis (RO) systems, it uses pressure to force tap water through a series of specialized filters. A 5-gallon tank on the floor holds the treated water until Turpin turns on a faucet at her kitchen sink or needs more ice from her refrigerator.
She paid a contractor thousands of dollars to install this system last year to reduce nitrates in her drinking water.
The difference is visible.
Turpin dipped a color-changing test strip into a glass of water from her kitchen faucet and another from a faucet in her basement. While the test strip in the RO water turned pale pink, the other looked like a raspberry stain, suggesting much higher levels of nitrate.
“[It] makes me very glad that I have the reverse osmosis system, and I have zero guilt about the money that I spent on that purchase,” Turpin said. “But it also makes me concerned for people that don't have it.”
Nitrates form naturally in the environment, and they’re an essential plant nutrient. But Iowa has excess amounts in its waterways, largely due to fertilizer, manure and a lack of perennial cover on a landscape once dominated by tallgrass prairie.
Nitrates that accumulate downstream can feed algal blooms and contaminate sources of drinking water.
Under federal law, public drinking water systems are required to keep nitrate-nitrogen concentrations below 10 milligrams per liter. It was set decades ago to prevent infant methemoglobinemia, a life-threatening blood disorder often called “blue baby syndrome.”
But research since then indicates long-term exposure at lower levels of nitrate in drinking water can increase risks for colorectal cancer, thyroid disease, neural tube defects and other adverse health effects.
The U.S. Environmental Protection Agency (EPA) began a health assessment of nitrate in 2010. However, it hasn’t moved beyond the first step in the process.
As a healthcare provider and someone concerned about Iowa’s rising cancer rates, Turpin said she’s been focusing more on prevention. She views RO as a way to reduce her own health risks as she ages and as a way to help protect her pets.
“I really started thinking about [reverse osmosis] more seriously last year,” Turpin said. “The talk about high nitrates in the water just became a much bigger part of the public conversation.”
Central Iowa Water Works (CIWW), the regional drinking water authority for nearly one in five Iowans, issued its first lawn water ban last year and another earlier this summer.
The restrictions weren’t caused by a lack of water. Rather, CIWW’s leaders said they needed to quickly cut consumer demand to keep pace with nitrate removal as levels spiked and stayed high in the Des Moines and Raccoon rivers.
The rivers are two of CIWW’s main sources for drinking water and often contain some of the highest nitrate levels in the U.S., according to the Central Iowa Source Water Resource Assessment.
“[T]he current situation is unique because nitrate concentrations have remained elevated throughout the winter and into 2026, with all available source waters experiencing elevated nitrate levels simultaneously for much of the year,” the press release stated.
While CIWW maintains it has not exceeded the EPA’s standard, researchers and policy experts say RO systems could help protect the health of individuals in central Iowa and other parts of the state where nitrates swing high for extended periods.
But the initial costs and ongoing maintenance of these systems could be out of reach for many, and they say it doesn’t solve the larger challenges with water quality in the state.
Concerns over nitrates and cancer
A week after record rainfall in parts of central Iowa, Colleen Fowle watched the swollen Des Moines River flow south of Saylorville Dam.
“Not only is it difficult to see through, and there’s lots of sediment, and trees and debris … but we also have those invisible chemicals,” Fowle said. “The runoff carries chemicals into the waterways.”
Fowle is the water program director for the Iowa Environmental Council, which has helped coordinate Cancer Community Conversations around the state since last year. She said in-home RO is something that comes up frequently during these meetings.
“I think that Iowans are now realizing some of the health effects that can be contributed from the poor water quality in the state, and so they're asking a lot of questions about how they can take matters into their own hands and reduce some of that exposure to create better public health outcomes for themselves and their families,” Fowle said.
Iowa has the second highest rate of cancer in the U.S. and is one of three states with rising rates.
While certain behaviors, like smoking and UV exposure, are well-established risks, researchers have identified environmental factors that may contribute to Iowa’s outlier status. This includes high levels of nitrate, radon, PFAS — known as “forever chemicals” — and pesticides.
The Center for Health Effects of Environmental Contamination (CHEEC) at the University of Iowa recommends Iowans test their homes for contaminants and work with trained technicians to install certified mitigation technologies, like reverse osmosis.
How does reverse osmosis work?
RO systems can significantly reduce potential contaminants, like nitrate, PFAS, lead, volatile organic compounds, microplastics and bacteria.
David Cwiertny, director of CHEEC and a professor of civil and environmental engineering and chemistry at the University of Iowa, described RO as straining spaghetti — but with a “very efficient filter.”
“You're allowing clean water to go through, and you're keeping all the things you don't want stuck behind that barrier,” Cwiertny said. “It is about the most effective treatment process we have for removing a wide range of chemical contaminants.”
A reverse osmosis system could drop nitrate levels below detection, Cwiertny said. But its effectiveness depends on the concentration in the tap water and whether the filters have been tested and certified by an accredited third party.
NSF/ANSI 58 is the national standard for nitrate reductions in point-of-use RO systems. Consumers can search NSF’s database for certified drinking water units and filters. The Water Quality Association also lists products that meet NSF standards.
Cwiertny said one downside to reverse osmosis is that it uses more water.
According to the EPA, a typical system connected to a single faucet can “generate 5 gallons or more of reject water for every gallon of treated water produced.” For perspective, the average American household uses more than 300 gallons of water per day, with showers and toilets accounting for nearly half.
Products with the EPA’s WaterSense® label must demonstrate they send no more than 2.3 gallons of wastewater down the drain for every gallon of treated water they produce.
While individuals can install systems themselves, Cwiertny recommended hiring a professional.
“That's probably the best way to go to ensure that it gets done right,” Cwiertny said. “One of the concerns over point-of-use is if they're not properly installed and people think they're getting this public health protection, and they're not.”
Steve Murtha, CEO of Culligan Des Moines, said he’s seen RO systems installed incorrectly in homes and filters without an NSF certification.
“That can be misleading for people,” Murtha said.
These systems also need routine maintenance, just like a car, Murtha said.
Generally, some filters need to be replaced every six to 12 months, while the semi-permeable RO membrane is every two to five years. The frequency depends on the model, along with the quality of the water and how much it uses.
“You’ll visit customers sometimes that haven’t changed filters in four or five years,” Murtha said. “Just because there’s water coming out of there doesn’t mean it’s working because your filter’s going to be shot and it’s not doing what’s it’s supposed to.”
Many of the companies that install reverse osmosis systems offer maintenance and testing services.
While DIY color-changing nitrate test strips have become popular, Cwiertny warns that different units for measuring nitrate can create confusion.
Products that measure "nitrate-nitrogen," like Hach’s nitrate and nitrite test strips, produce results that are comparable to the EPA's public drinking water standards. Using test kits that measure only "nitrate" would require a conversion.
The DIY test strips also leave “a lot of room for misinterpretation,” he said. Researchers say they’re best treated as screening tools.
“Nothing's as accurate as collecting a water sample, sending it to a lab like the State Hygienic Lab or to us at CHEEC, running it on analytical instrumentation using an EPA-approved method and getting a number,” Cwiertny said.
The State Hygienic Lab tests water samples on a fee-for-service basis. CHEEC provides similar services and offers free- or reduced-prices for private well owners, Cwiertny said. Unlike public water systems, private wells are not regulated under the Safe Drinking Water Act.
Affordability and the bigger picture
The Iowa Environmental Council (IEC) believes reverse osmosis systems “can play an important role in public health by providing an immediate exposure reduction,” Fowle said.
But Fowle and her colleagues worry about the financial barriers for some Iowans.
“The cost of purchasing and installing and maintaining equipment like this is beyond the reach of many families in Iowa, and so that sets up inequities between the families that can afford it and the families that cannot,” she said.
The cost of in-home RO can swing from a few hundred to thousands of dollars. The price depends on the model, whether it’s a whole-house or faucet-specific unit and whether someone is hiring a contractor to install it.
Drilling through floors or cabinets and the location of the water feed and drain can also affect the installation cost.
IEC and its partners on a recent report, Environmental Risk Factors and Iowa’s Cancer Crisis, recommend expanding the state's Private Wells Grant Program. Low-income residents with contaminated wells could qualify for a free or subsidized water treatment system, like reverse osmosis.
Other states already do this, Fowle said.
Wisconsin has a private well testing and compensation program, and Minnesota provides something similar for eight counties in the southeast part of the state. Nebraska offers a tax credit for reverse osmosis.
While much of the focus on nitrates has been on the Des Moines area and CIWW, Fowle said smaller utilities around the state are struggling.
“We really need to think about eliminating the pollution to begin with, rather than asking downstream users to modify their drinking water systems,” Fowle said.
Roughly 93% of total nitrogen loads in Iowa’s waterways comes from nonpoint sources, according to the Iowa Nutrient Reduction Strategy. It outlines a suite of voluntary agricultural practices, like cover crops, wetlands and saturated buffers, to reduce nitrogen loss.
“We need to take a hard look at what is happening in our individual watersheds,” Fowle said. “We have the technology to map all of the watersheds in Iowa and determine through that modeling technology where the sources of the pollution are coming from and what practices we can put in specific locations in order to reduce that.”
Calibrating those models requires a robust water quality monitoring network, Fowle added.
“We really need to use science, data and technology in order to determine where to best spend our dollars,” she said. “We also need leadership in the state to admit this is an issue and continue to work together with all parties.”
Fowle emphasized there are solutions to improve the state’s water quality and its residents’ health.
With both candidates for governor talking about these issues, Fowle is hopeful 2026 could be the “turning point that Iowa has been waiting for.”
