Do You Even Need a Water Filter? (Most People Don't)
Every U.S. drinking-water rule comes with two numbers: a health goal (the MCLG, the level at which a contaminant causes no known harm) and a legal limit (the MCL, the level your utility must not exceed). They are set apart on purpose, and sometimes they are far apart — so 'legal' and 'safe' are not the same reading. The video walks through how to find both numbers for your own tap.
For most households the honest answer is that you do not need a filter — your utility already treats the water to meet federal limits. But some taps genuinely warrant one, and a short four-question checklist (your utility's latest report, your area's known contaminants, your home's plumbing age, and whether you have a lead service line) tells you which group you are in without guessing.
If you do filter, the only promise that gets independently verified is the NSF/ANSI number on the box — 42 for taste and chlorine, 53 for health contaminants like lead, 58 for reverse-osmosis systems. Match the certification to the specific contaminant in your water rather than buying on brand claims.
Do you need a filter? The four-question test
Have you read your utility's latest water quality report?
Every U.S. utility publishes an annual report (the CCR) listing what was detected in your water and how it compares to federal limits. That report — not a sales pitch — is where the answer starts. Our city pages compile the same utility-reported data so you can look yours up by city.
Does your area have known contaminants sitting between the health goal and the legal limit?
Water can be fully legal and still carry contaminants above the health goal (MCLG). Phoenix, for example, averages 5.4 ppb arsenic — under the 10 ppb legal limit, but above the 0 ppb health goal. If your city has a gap like that, a certified filter is a reasonable choice, not paranoia.
How old is your home's plumbing?
Everything your utility reports is measured before the water reaches your street. Older pipes, fixtures, and solder inside your own home can add lead or copper after that point — a risk no city-level report can see.
Do you have (or might you have) a lead service line?
The service line is the pipe connecting your home to the water main. If yours is lead — or you can't rule it out — a filter certified for lead removal (NSF/ANSI 53) is warranted regardless of how clean your utility's numbers look.
Key takeaways
- 'Legal' and 'safe' are two separate numbers: the enforceable MCL versus the health-based MCLG, which can differ by design.
- Most people do not need a water filter — a four-question checklist (utility report, local contaminants, plumbing age, lead service line) tells you if you are the exception.
- Boiling does not purify tap water; for chemicals like arsenic or PFAS it can concentrate them.
- PFAS 'forever chemicals' turned up in at least 45% of U.S. tap-water samples in a national USGS study, and a 2024 EPA rule sets the first federal limits.
- If you filter, match the NSF/ANSI certification (42, 53, or 58) to the contaminant you actually have.
Common questions
Is tap water safe to drink?
For most U.S. households, yes — utilities are required to treat water to meet federal legal limits and publish their results every year. But 'legal' and 'safe' are two different numbers by design: the enforceable limit (MCL) can sit well above the health goal (MCLG). The honest answer is local, so check your own utility's numbers rather than trusting a blanket yes or no.
Is sink water safe to drink?
Sink water is tap water — your kitchen and bathroom taps draw from the same municipal supply. What can differ inside one home is the plumbing: older pipes, fixtures, or a lead service line can add contaminants after the water passes the meter, which is exactly what the plumbing questions in the checklist above screen for.
Is tap water bad for you?
Not for most people, most places. The useful question is which contaminants your local supply actually carries and at what levels — a USGS study detected PFAS 'forever chemicals' in at least 45% of U.S. tap-water samples, but levels vary enormously by location. Look up your city's utility-reported data instead of settling for a nationwide average.
Does boiling tap water make it safe?
No — boiling kills microbes, but it does not remove chemical contaminants like arsenic, lead, or PFAS. Because some water evaporates while boiling, it can actually concentrate them slightly. For chemical contaminants the only home fix that works is a filter certified for that specific contaminant.
Do water filters actually work?
Certified ones do — for the contaminants they're certified against. The only independently verified promise on the box is the NSF/ANSI number: 42 for taste and chlorine, 53 for health contaminants like lead, 58 for reverse-osmosis systems. Independent testing of home filters shows performance varies widely between products, so match the certification to the contaminant in your water rather than buying on brand claims.
How do I find out what's in my tap water?
Start with your utility's annual water quality report (CCR) — it's the primary source, and our city pages compile the same utility-reported data in a searchable form. If your concern is your own home's plumbing or a private well, an accredited-lab water test is the definitive answer because it measures your tap, not the system average.
Sources
- TapWaterData — Phoenix, AZ water quality (arsenic 5.4 ppb demo)
- EPA — Drinking Water Arsenic Rule History (10 ppb limit)
- EPA — PFAS National Primary Drinking Water Regulation (2024)
- USGS — PFAS detected in tap water across the US (2023 study)
- Duke/NC State — Home water filter PFAS study (ES&T Letters, 2020)
- NSF/ANSI — Standards 42, 53, and 401 for filtration systems
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