Clean Water

If you’re wondering whether your water is part of the picture, the CDC suggests testing it before choosing a filter ^[4]. Our family’s own changes included reverse-osmosis drinking water and a filtered shower; you can read about it in our story. This guide explains how to find out what’s in your water and how to match a filter to it, based on CDC, EPA and NSF guidance.

Step 1: Find out what’s in your water

If you’re on public (city) water

• The EPA requires community water systems to deliver a Consumer Confidence Report, an annual drinking water quality report, by July 1 each year ^[1].
• The CDC says this report will show if there are harmful germs or chemicals in your water ^[4].
• You can also look up your utility by ZIP code in the EWG Tap Water Database, a free tool from the nonprofit Environmental Working Group (EWG) ^{[6, 7]}. It compiles water systems’ own test results (mostly from 2021 to 2023 in the current edition) and compares them with EWG’s own health guidelines, which are often stricter than EPA’s legal limits ^{[6, 7]}.
• EPA sets its enforceable limits as close to its health goals as possible while also weighing cost and treatment technology ^[3]; EWG’s guidelines are based on health alone ^[7]. So a utility can meet every legal limit and still be above an EWG guideline ^[6]. Your Consumer Confidence Report is still the report your utility is required to send you each year ^[1], and the database doesn’t cover private wells ^[7].
• Taste, smell and appearance are not always good signs of water safety: harmful germs and chemicals often don’t change how water looks, tastes or smells ^[4].

If you have a private well

• As a well owner, you are responsible for testing ^[2]. EPA rules that protect public water systems don’t apply to private wells, and government officials don’t regulate, treat or monitor them ^[2].
• Test at least once a year for total coliform bacteria, nitrates, total dissolved solids and pH ^{[2, 8]}.
• Ask your health department what else to test for where you live, and use a state-certified laboratory ^[2].
• Test more often or for more contaminants if you suspect a problem or notice changes in color, taste or smell ^{[4, 8]}.
• High levels of nitrates can make people sick, especially babies ^[2]. Nitrates can come from animal waste, septic systems, fertilizers and farm runoff ^[2].
• The EPA suggests testing more often if small children or older adults live in the home, or if someone is pregnant or nursing ^[8].
• After flooding or another natural disaster, contact your local or state health department for advice on inspecting and testing your well ^[8].

Step 2: Check for lead

• Where it comes from: the most common sources of lead in drinking water are lead pipes, faucets and fixtures ^[3]. In homes with lead service lines, the pipes connecting the home to the water main, these are typically the most significant source ^[3].
• Which homes: lead pipes are more likely in older cities and in homes built before 1986 ^[3]. In homes without lead service lines, the most common problem is brass or chrome-plated brass faucets and plumbing with lead solder ^[3].
• How many: the EPA estimates about 4 million lead service lines serve properties across the U.S. and has set a goal of replacing all of them ^[9].
• What helps now: use only cold water for drinking, cooking and making baby formula ^[3]. Boiling water does not remove lead ^[3]. Run the tap before drinking when water has been sitting in the pipes ^[3].
• Filters: if you use one, make sure it is certified to remove lead, and replace the cartridge as directed ^[3].
• Blood testing: a blood lead test is the best way to find out whether a child has lead poisoning ^[10]. See our heavy metals guide.

Step 3: Understand filter types and certifications

The CDC says what a filter removes depends on the size of its pores, the size of the substance and the substance’s electric charge ^[4]. Filters that remove germs often don’t remove chemicals, and vice versa, so always check the label ^[4].

What the NSF/ANSI standards mean

NSF is an independent organization that develops public health standards, and you can look up certified products in its database ^[4].

• NSF/ANSI 42: reduces aesthetic impurities such as chlorine, taste and odor ^[5].
• NSF/ANSI 53: reduces a specific contaminant with a health effect, as regulated by the EPA and Health Canada ^[5]. For PFAS, the EPA points to NSF/ANSI 53 or 58 certification ^[11].
• NSF/ANSI 58: reverse osmosis systems, which push water through a semi-permeable membrane to reduce regulated contaminants ^[5].
• NSF/ANSI 401: reduces one or more of 15 “emerging contaminants,” such as some pharmaceuticals and chemicals not yet regulated ^[5].

Certification is specific to listed contaminants: the EPA advises checking NSF’s website to see whether a product treats the particular PFAS you want to remove ^[11].

Common filter types

• Pitcher and refrigerator filters often use activated carbon ^[4]. Their main purpose is to improve taste and smell rather than safety ^[4]. Most home filters like these are not designed to remove germs ^[4].
• Reverse osmosis has a pore size of about 0.0001 micron ^[12]. It removes parasites, bacteria and viruses and some chemicals, including lead, copper, chromium, chloride and sodium ^[12]. It also sends untreated water down the drain, about a gallon for every gallon treated ^[11].
• PFAS: the EPA found that activated carbon, ion exchange and reverse osmosis systems it studied can greatly reduce PFAS ^[11]. Look for NSF/ANSI 53 or 58 certification for PFAS reduction ^[11]. As of April 2024, those certifications didn’t yet show removal down to EPA’s new drinking water limits ^[11].

Trade-offs to know

• Filters remove good and bad substances, including chlorine, which kills germs, and fluoride, which prevents cavities ^[4].
• Whole-home filters that remove chlorine can let more germs grow in your plumbing ^[4].
• Every filter needs maintenance ^[4]. Change cartridges as recommended to keep it working and prevent germ growth ^[4]. Filters only work if they are maintained according to the manufacturer’s instructions ^[11].
• If your immune system is weakened, the CDC suggests a system that removes Cryptosporidium and having someone else change filters ^[4].

Shower filters: what the evidence shows

• What certification covers: NSF/ANSI 177 shower filters are “certified to only reduce free available chlorine” ^[5]. Evidence: the standard makes no health claims.
• Whole-home option: the CDC suggests whole-home (point-of-entry) filters if you need to remove a harmful substance, such as certain volatile organic chemicals, from all your water, including the water you bathe in ^[4].
• If you use one: look for an NSF/ANSI 177 certification to confirm its chlorine-reduction claim ^[5]. We didn’t find good evidence that shower filters improve health conditions.

What to do next

General information, not a diagnosis or a treatment plan. A licensed clinician can tell you which of these steps fit you.

1. Step 1Start this week

   • Find your Consumer Confidence Report with EPA’s online search tool ^[1].
   • On public water, you can also look up your utility by ZIP code in the EWG Tap Water Database to see how its results compare with EWG’s health guidelines ^[6].
   • If you have a well, schedule a test with a state-certified lab ^[2].
   • Check whether your home was built before 1986 or has lead plumbing ^[3].

2. Step 2Decide what, if anything, to remove

   • Match a filter to the specific contaminants you found; if your water is free of harmful germs and chemicals, you may not need one ^[4].
   • Look up products in NSF’s database to confirm what they’re certified to remove ^[4]. Evidence: CDC and EPA guidance.

3. Step 3Maintain what you choose

   • Change cartridges on schedule; wear gloves and wash your hands afterward ^[4].

4. Step 4If lead or other contaminants are found

   • Use cold water for drinking and cooking, use a lead-certified filter, and contact your water system and health department ^[3].
   • Ask your doctor about a blood lead test for children who may be exposed ^[10].

Questions to ask your water utility or lab

• Is there a lead service line at my address, and when is it scheduled for replacement?
• What did the latest Consumer Confidence Report find for lead, PFAS or other contaminants?
• For my well, what should I test for in this area, and which certified lab should I use?
• Which filter certification matches the contaminants found in my water?
• How often should I retest, especially after flooding or plumbing work?

Sources

Numbers in brackets in the text link to these sources. Links were checked in October 2026. Some sources are written by people who support a particular approach; we've tried to say so in the text.

1. EPA. CCR Information for Consumers. Web page, accessed October 18, 2026. https://www.epa.gov/ccr/ccr-information-consumers
2. CDC. Guidelines for Testing Well Water. Web page, accessed October 18, 2026. https://www.cdc.gov/drinking-water/safety/guidelines-for-testing-well-water.html
3. EPA. Basic Information about Lead in Drinking Water. Web page, accessed October 18, 2026. https://www.epa.gov/ground-water-and-drinking-water/basic-information-about-lead-drinking-water
4. CDC. About Choosing Home Water Filters. Web page, accessed October 18, 2026. https://www.cdc.gov/drinking-water/prevention/about-choosing-home-water-filters.html
5. NSF. NSF Standards for Water Treatment Systems. Web page, accessed October 18, 2026. https://www.nsf.org/consumer-resources/articles/standards-water-treatment-systems
6. Environmental Working Group (EWG). EWG Tap Water Database: FAQs. Web page, accessed October 18, 2026. https://www.ewg.org/tapwater/FAQ.php
7. Environmental Working Group (EWG). EWG Tap Water Database: Methodology. February 2025. Web page, accessed October 18, 2026. https://www.ewg.org/tapwater/methodology.php
8. EPA. Protect Your Home’s Water. Web page, accessed October 18, 2026. https://www.epa.gov/privatewells/protect-your-homes-water
9. EPA. Lead Service Lines. Web page, accessed October 18, 2026. https://www.epa.gov/ground-water-and-drinking-water/lead-service-lines
10. CDC. Testing for Lead Poisoning in Children. Web page, accessed October 18, 2026. https://www.cdc.gov/lead-prevention/testing/index.html
11. EPA. Identifying Drinking Water Filters Certified to Reduce PFAS. Web page, accessed October 18, 2026. https://www.epa.gov/water-research/identifying-drinking-water-filters-certified-reduce-pfas
12. CDC. About Home Water Treatment Systems. Web page, accessed October 18, 2026. https://www.cdc.gov/drinking-water/about/about-home-water-treatment-systems.html