How to Decode What’s in the Water You Drink and Cook With

Your tap water can taste great and look crystal clear, and it can still contain contaminants harmful to your health. Many of these harmful chemicals can’t be seen, smelled, or tasted. 

While cities and towns often treat and test the public water supply, factors like how far the water travels from the treatment facility to your home, nearby industrial zones, the age of pipes running to your home, and the plumbing and fixtures in your home can all impact what’s in your water and increase your exposure to potentially harmful contaminants. 

At-home water testing kits can identify and quantify  a host of chemicals in your tap water. This data can take the guesswork out of what’s coming from your tap, providing information you can use to protect your family’s health. 

“People track their steps, nutrition, and sleep, so it makes sense to have data on your water, especially considering it’s critical to so many parts of life,” says Agustin Pierri, technical director of WEC Labs.

What’s in my water? 

While many cities and towns treat and publicly disclose water test results to the community, what the city reports and treats isn’t necessarily representative of what you drink. A lot can happen in between the treatment plant and your tap. 

In some areas with city water, water travels hundreds of miles through pipes, which could introduce contaminants. “These pipes could be old and when they're old, they could have deposits of minerals built up in them that could leach back into the drinking water,” says Rick Andrew, water filtration expert, former NSF employee, and ROSE scientific advisory board member. If you live in an older home, he adds, the pipes running to your home from the street or the plumbing in your house could also introduce lead or other heavy metals into your water. 

And while cities treat the water supply with disinfectants, these treatments don’t always cover the most concerning chemicals. 

For example: PFAS, known as forever chemicals due to their chemical stability, can travel through water deposits, precipitation, or as a gas and are found throughout the world, even in areas uninhabited by humans. As a result, these chemicals easily enter bodies of water, soil, and can easily enter water treatment plants. 

“Not all of the treatments done at those facilities fully capture or destroy the PFAS,” says Lydia Jahl, senior environmental scientist and ROSE Home advisory board member. Further, Pierri says public water suppliers don't test for some emerging and harmful chemicals, including a disinfection byproduct called iodoacetic acid. While it’s important for suppliers to treat water, byproducts of common disinfectants are linked with negative health outcomes, including an increased risk of cancer. (More on that later.)

If your water comes from a well, your local water authority likely isn’t responsible for testing it for potentially harmful chemicals. “If there’s a factory nearby that’s polluting a local river, then that gets in the groundwater, and the well is directly exposed to those,” says Jahl. 

While any contaminated water exposure can be harmful, including the water used to wash your dishes and that you bathe in, drinking and cooking water are a major concern. It goes straight into your digestive system,” says Andrew. Consuming this water is especially problematic for families with babies (especially those who drink formula) and young children, who Andrew says are more impacted by harmful chemicals. 

As technology emerges, at-home water testing kits can identify more and more chemicals in water, not just ones regulated by the EPA, so you can take action to filter out harmful chemicals. “By knowing directly, you can take a step of figuring out the proper water filtration system that matches well to the chemicals in your water to ensure they’re removed,” says Jahl.

Common water contaminants 

The major water contaminant classes ROSE Home tests for in water all have distinct sources and impact. Below, learn more about what may be in your water and its potential health effects.

PFAS

Per- and polyfluoroalkyl substances, or PFAS, are industrial, man-made chemicals commonly used in personal care products, upholstery treatments, and nonstick cookware. Because they are created to make these things stain-, oil-, heat-, and water-resistant, they don’t easily break down and can live in your body for years (hence the name “forever chemicals”). 

“So they exist in the environment and in your body for a long time,” says Jahl.

PFAS can enter lakes, rivers, and groundwater when they're released from manufacturing facilities, landfills, wastewater treatment plants, or products that contain these chemicals. Because PFAS break down very slowly, they can persist in the environment indefinitely, allowing them to spread into sources of drinking water or the water we shower and bathe in.

They’re known to cause many different negative health impacts. One review, published in 2021, highlighted links between PFAS and developmental delays, changes in thyroid function, liver disease, reduced immune system responses, hormone problems, and cancer. “Because they stick around in our bodies for so long, we really want to prevent them from getting into the body in the first place,” says Jahl. 

Disinfection byproducts

Many water treatment facilities use specialized disinfectants to ensure clean water supply and prevent the spread of infectious disease. But the byproducts produced by this safety measure can introduce unintended harm. 

Disinfection byproducts are formed when disinfectants, especially chlorine, react with the natural organic matter found in water. “We need these disinfectants, but we also need to be cognizant of when concentrations of these byproducts are so high they become a concern,” says Adelina Voutchkova-Kostal, Director for Sustainable Development at the American Chemical Society and member of the Advisory Board for ROSE. 

Some evidence links chronic exposure to disinfection byproducts, specifically trihalomethanes (THMs), with an increased risk of certain cancers, such as bladder cancer and possibly colon cancer in men, though this data is emerging. A systematic review suggested that people who lived in areas with higher levels of THMs had a small but real increase in bladder cancer risk, compared with people in areas with lower THM levels.

Studies have also found exposure to high levels of certain disinfection byproducts during pregnancy is associated with an increased risk of miscarriage, neural tube defects, and low birth weight, though this risk may not be present at lower levels.

Heavy metals

Heavy metals are naturally occurring elements present in the earth’s crust. While certain heavy metals, such as iron and zinc, are essential and play an important role in human health, heavy metals such as lead, arsenic, mercury, and cadmium, can be toxic even in small amounts. 

Heavy metals can enter drinking water through natural deposits in rocks and soil, as well as from industrial pollution, mining, agricultural runoff, and corrosion of older pipes and plumbing fixtures. 

Lead pipes are a well known example of heavy metal harm. While the installation of new lead pipes has been outlawed in the United States since 1986, and the EPA in 2024 passed the Lead and Copper Rule stating these service lines must be replaced by 2034, Pierri says many older homes still may have distribution lines that are either made of or soldered with lead. “You can’t feasibly replace millions of lead service lines in the United States, so it’s important to test for it, especially in older homes.”

Heavy metals can cause significant short-term and long-term health risks, Voutchkova-Kostal says, depending on the length and type of exposure and the specific metal. They’re shown to accumulate in organs, so they can cause organ damage. Studies also link heavy metal exposure to cardiovascular, respiratory, and neurological problems, and some are classified carcinogens. According to Pierri, heavy metals can be particularly problematic for pregnant women and children. According to the Centers for Disease Control and Prevention, lead stored in the bones of pregnant women can release into the blood during pregnancy, increasing the risk of miscarriage or harm to the baby’s kidneys, brain and nervous system.

VOCs

Volatile organic compounds, or VOCs, are chemicals that can vaporize into the air and dissolve in water. They exist throughout the environment and are commonly used in industry, agriculture, and around the home, found in everyday products including gasoline, paint, varnish, adhesives, cleaning products, and perfumes. Improper disposal, leaks from underground storage tanks and pipelines, industrial spills, and runoff can allow VOCs to seep through soil and contaminate groundwater. If they’re released into groundwater, VOCs can end up in the drinking water supply.

In one study of more than 2,000 domestic wells, VOCs were present in 65% of samples, with 1.2% of samples above the EPA maximum contaminant levelToxic levels of VOCs have been linked in research to liver problems, lung cancer, and reproductive concerns, including miscarriage and stillbirth.

Pesticides

Pesticides are substances used to prevent or destroy any type of pest. Pesticide runoff from farmland can wash into nearby streams, rivers, and lakes during rainfall or irrigation, while some pesticides can also seep through soil into groundwater that supplies drinking water. Pesticide runoff is most common in agricultural regions, such as the Midwest corn belt, Central Valley, and the Mississippi River basin. 

Years of studies confirm the health impacts of pesticide exposure. Along with a heightened risk of neurological disorders, including Alzheimer’s, pesticides are also shown to increase the risk of certain types of cancer. Though it is unknown at what level pesticides become toxic, studies have shown certain groups, such as agricultural workers, have a higher risk of disease.. 

Practical steps for safer water

There’s a lot you can do to make sure your water’s safe. Here’s where to start.

Understand what’s in your water

Before you take any action, it’s critical to understand what’s actually in your water. People who are on a public water supply can double check their Consumer Confidence Report to learn more about the source of their drinking water, the way it is treated, and any contaminants detected in it. You can find your local report at CCR Information for Consumers. 

That said: This information is only a starting point, especially because so much can change between your water supply and the tap. If your goal is to prevent potentially harmful chemicals in your tap water, a comprehensive water test is essential. After all, you can't solve a problem you haven't measured. 

Many types of water tests are available. For the most precise, actionable results, Andrew recommends a laboratory test kit. These tests involve sending samples of water to a lab which carefully analyze them using evidence-based tools. “This type of test can be very valuable because it gives you information on such a broad array of contaminants,” says Andrew. “This information can then inform your water treatment decision.” 

Routine testing over time can be a helpful strategy. “As the water supply changes, things can happen on the distribution side that the municipality may not know about,” says Pierri. For example, your local water provider could increase the dosage of a disinfectant, which could alter your tap water. Or the protective coating inside your water service line could wear away, causing metal to leach into your tap. 

Choose a filter that targets those contaminants

Not all water filters are created equal, so it’s important to find one that addresses the specific contaminants in your water. Each type of filter system has its own pros and cons, including installation, maintenance, and cost. When you’re considering a water filter, budget is an important factor. 

According to Andrew, you can find plenty of effective filtration solutions in a lower price range, but it’s important to be aware of the limitations of certain filters. For example, pitchers and carafes can be cost effective, but they require frequent filter changes to work effectively. “If the filter is saturated with contaminants, they leach back out into the water,” says Pierri. 

Along with looking for a filter that eliminates the specific chemicals present in your water supply, Andrew suggests looking for a filter that’s certified by NSF, WQA, and/or IAPMO. Not sure where to start? Here are common water filter options to explore:

• Pitchers and carafes: These filters work by passing water through a replaceable filter, making them one of the easiest and most affordable options with no installation required. The tradeoff is that they filter water relatively slowly and often require more frequent filter replacements than larger systems.

• Countertop filters: These units connect directly to your faucet and sit on the countertop, filtering water as it flows through the system. While they require no installation, they also take up counter space. 

• Under-sink filters: These systems, which are installed beneath the sink, filter water before it reaches a dedicated drinking-water faucet or the existing faucet. They don’t occupy valuable counter real estate, but they may require installing an auxiliary faucet (which could mean drilling through a countertop). 

• Reverse osmosis: Reverse osmosis systems force water through a very fine membrane that can filter out a wide range of contaminants, including lead, arsenic, nitrates, and PFAS. They provide some of the most comprehensive filtration available, though they may require professional installation and produce wastewater during filtration. Some reverse osmosis systems also add small amounts of minerals like calcium and magnesium back into the water to improve its taste.

• Whole-house filters: Whole-house filtration systems treat water as it enters the home, so filtered water flows to every faucet and appliance. Depending on the system, they can reduce contaminants such as sediment, chlorine, rust, volatile organic compounds (VOCs), and some other chemicals. Some specialized systems are also designed to reduce contaminants like iron, sulfur, or PFAS, but not all whole-house filters remove these. 

While they're excellent for improving overall water quality, Andrew says they're generally not recommended as the primary solution for homes with older pipes and plumbing that may contain lead, because contamination can enter the water downstream of the treatment system and be present at the tap, where drinking water is consumed.

• Water softener: Unlike traditional water filters, water softeners don't remove contaminants. They use ion exchange to replace calcium and magnesium (the minerals that cause hard water) with sodium or potassium. (Some studies show water softeners that replace fluoride can decrease enamel strength on teeth, so consider your water softener doesn’t replace this mineral. Most standard models don’t.) They're a good option if hard water is causing scale buildup, dry skin, or damage to appliances, but they should be paired with a certified drinking water filter if your goal is to remove contaminants like lead, PFAS, or pesticides.

The most important factor is choosing a product that actually reduces the contaminants you’re concerned about, which is why testing prior to purchase is essential. 

Consider fixture or pipe replacement 

It’s possible that contaminants could be coming from the pipes or fixtures in a house, but in many houses it can be very difficult to know if that is the case. “Contaminants such as lead that could come from the pipes in the house could also come from the water distribution system or the service line from the street to the house,” says Andrew. So, in many cases, there’s no reliable way to be sure replacing the pipes would solve the problem. 

If you have the ability to test the water right when it enters the home from the main supply and then again at the tap, and you find contaminants in the tap water that weren’t present in the first sample, then Andrew says it’s possible that they’re a result of the home’s pipes. In these cases, if there is substantial evidence that the contaminants are coming from the pipes in the house, then replacing those pipes could solve the problem.

Summary 

The more information you have about your tap water, the better decisions you can make. And many effective, affordable water filtration solutions exist. 

“Your water could be perfectly fine, but it may not be, and knowledge is power,” says Andrew. “Once you have knowledge and understanding of what you're dealing with, then you can start to take the steps to implementing a solution.” 

FAQ

Are there PFAS in tap water?

Possibly. PFAS ("forever chemicals") are widespread enough that they fall from clouds as precipitation and easily enter water supplies. Not every treatment facility captures or destroys PFAS, and public suppliers often don't test for every emerging contaminant. Testing your own water is the most reliable way to check for PFAS contamination in your tap.

How do I test my tap water at home?

An at-home water testing kit like the ROSE testing kit gives the most precise read on what's actually coming out of your tap. Unlike a public water report, which only reflects conditions at the treatment plant, home testing accounts for what your water picks up on its way through aging pipes and home plumbing.

Do I need a home water lead test if my water comes from the city?

Yes. Municipal treatment doesn't account for lead leaching from old pipes, service lines, or fixtures between the treatment plant and your tap. 

Can a water filter remove PFAS?

Some can, not all. Look for filters certified by NSF, WQA, or IAPMO, and match the filter to what your test results actually show.

Is well water tested for contaminants?

Not automatically. Private wells generally fall outside a local water authority's testing responsibility, so well owners have to test on their own.