Independent tap water research

Know what’s in your tap water before anyone sells you a filter.

City-by-city readings from national testing by the U.S. Environmental Protection Agency (EPA) and each utility’s own report: hardness, PFAS (“forever chemicals”), disinfectant and violations, plus what each one means for softeners and filters. Every number is sourced and dated.

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40 water systems · EPA data through September 2026

How hard is the water? 40 large US systems

Dot size: people served

SoftModerately hardHardVery hardNot published

Numbers beside labeled cities are grains per gallon. 34 of 40 utilities publish hardness; source for each is on its city page.

Short answer

Of the 34 systems we cover whose utilities publish hardness, Indianapolis has the hardest tap water at about 18.5 grains per gallon and Portland the softest at about 0.5. The U.S. Environmental Protection Agency’s (EPA’s) 2023–25 testing found PFOA or PFOS (two PFAS “forever chemicals”) above its 4 parts per trillion (ppt) limit in samples from Miami, Philadelphia, Dallas, Columbus, Austin, San Jose, Fort Worth, Louisville, Cincinnati, El Paso and Tampa. Lithium was above EPA’s health reference level in Los Angeles, Houston, San Antonio, Phoenix, Las Vegas, San Diego, El Paso, Tucson, Oklahoma City, Albuquerque and Kansas City. Hardness decides whether you need a softener; PFAS and disinfectant decide which filter.

EPA UCMR 5 (2023–25 sampling), EPA SDWIS 2026Q3, utility water quality reports · Sources and method

01 · Guides and research

What the readings mean, and what to do about them

Softeners

Water softeners, explainedHow a water softener works, the hardness level where one starts to make sense, what it fixes and doesn’t, the main types, and what they cost to buy and run.Salt-free vs. salt-basedHow salt-free conditioners and salt-based softeners differ, what independent scale tests found, what each costs, and where salt-based units are restricted.Softener sizing calculatorSize a water softener from your water’s hardness and your household’s water use: a calculator, the formula, and how to measure what you actually use.Water softener costWhat whole-house water softeners sell for, from online brands’ own stores and dealer brands’ published ranges, plus salt-free systems, filters and upkeep.Softener installation costWhat installing a water softener involves, which brands sell for do-it-yourself installs, what plumbers earn, and what dealer prices include.Dealer softener pricesWhat Culligan, Kinetico, RainSoft and EcoWater publish about softener prices, how each sells, their stated warranties, and how to compare a dealer’s quote.

Filters

Whole-house filter costWhat whole-house water filters sell for, from cartridge systems to carbon tanks and dealer installs, what they remove, and which appear in certification listings.Under-sink filters and ROHow under-sink carbon filters and reverse osmosis systems differ, what they sell for, and which models appear in NSF and WQA listings for PFOA and PFOS.Whole-house reverse osmosisHow whole-house reverse osmosis works, what it needs in space, power, drains and pre-treatment, how much water it sends down the drain, and store prices.Well water filtrationWhich treatment fixes each well water problem: iron, rotten-egg smell, hardness, bacteria, acidic water, nitrate and arsenic, with store prices for each.

Water quality

Hard water, explainedWhat water hardness measures, how to convert grains per gallon and mg/L, the USGS hardness scale, and the hardness level where a softener starts to pay off.EPA’s PFAS rule, explainedWhat EPA’s 2024 rule on PFAS, the “forever chemicals,” requires of water utilities, what EPA proposed to change in 2026, and how to read your city’s result.Chlorine vs. chloramineWhy utilities add chlorine or chloramine, how to tell which one your water has, and which filters remove each one.

Testing

Well water testingEPA’s checklist for testing a private well: the four things to test every year, when to test right away, and how to find a certified lab.How to test water hardnessFour ways to get your water’s hardness number, from free to lab-grade, how to read the result in grains per gallon or mg/L, and where to take the sample.

Research

Hard water and your healthEczema, hair, heart, kidney stones, sodium from softeners, appliances and pets PFAS and your healthWhat EPA, the National Academies and the WHO’s cancer agency found, and why the limit is 4 parts per trillion Lithium in tap waterWhy EPA tests for it, how its screening level was set, and the mental-health studies Chlorine and chloramineWhat agencies say, and what happens with dialysis, fish tanks and skin complaints

All guides →

02 · Hardness

Every city’s hardness, hardest first

Hardness decides whether a softener is worth buying. Each figure is from the utility’s own report; where it publishes a range, the outline shows it.

Hardness, by city

0 to 300 mg/L as calcium carbonate

Each dot is the utility’s published average or range midpoint; the outline shows its published range. Classes per USGS. Source: each utility’s latest water quality report.

Use this chart:Download imageFree to reuse with credit (CC BY 4.0).

03 · The cities

Every city, side by side

One row per water system. Tap a city for its full report: the source, who else drinks the same water, and what fits it.

City	Hardnessgpg	Hardness class	Disinfectant	PFOA highppt	PFOS highppt	Lithium highµg/L	Health violations5 years
Albuquerque, NM	8.8	Hard	Free chlorine	none	none	71	0
Atlanta, GA	not published		Free chlorine	none	none	none	0
Austin, TX	5.4	Moderately hard	Chloramine	none	4.8	none	1
Baltimore, MD	5.5	Moderately hard	Free chlorine	none	none	none	3
Boston, MA	0.9	Soft	Chloramine	none	none	none	0
Charlotte, NC	1.9	Soft	Free chlorine	none	none	none	0
Chicago, IL	not published		Free chlorine	none	none	none	0
Cincinnati, OH	7.5	Hard	Free chlorine	none	6.1	none	0
Cleveland, OH	6.8	Moderately hard	Free chlorine	none	none	none	0
Columbus, OH	6.7	Moderately hard	Free chlorine	5.3	none	none	0
Dallas, TX	8.0	Hard	Chloramine	6.3	5.1	none	0
Denver, CO	6.1	Moderately hard	Chloramine	none	none	11	0
Detroit, MI	6.3	Moderately hard	Free chlorine	none	none	none	0
El Paso, TX	10.2	Hard	Free chlorine	none	8.5	133	0
Fort Worth, TX	7.5	Hard	Chloramine	8.3	7.3	none	0
Houston, TX	7.9	Hard	Chloramine	none	none	34	1
Indianapolis, IN	18.5	Very hard	Chloramine	none	none	none	0
Jacksonville, FL	14.4	Very hard	Free chlorine	none	none	14	0
Kansas City, MO	5.8	Moderately hard	Chloramine	none	none	59	0
Las Vegas, NV	16.4	Very hard	Free chlorine	none	none	43	0
Los Angeles, CA	7.5	Hard	Chloramine	none	none	100	0
Louisville, KY	7.5	Hard	Chloramine	7.5	none	none	0
Memphis, TN	2.8	Soft	Free chlorine	none	none	none	0
Miami, FL	not published		Chloramine	14.0	33.0	none	0
Milwaukee, WI	8.1	Hard	Chloramine	none	none	none	0
Minneapolis, MN	5.5	Moderately hard	Chloramine	none	none	none	0
Nashville, TN	5.9	Moderately hard	Free chlorine	none	none	none	0
New York, NY	1.9	Soft	Free chlorine	none	none	none	0
Oklahoma City, OK	not published		Chloramine	none	none	68	0
Philadelphia, PA	8.9	Hard	Chloramine	8.1	6.0	none	0
Phoenix, AZ	not published		Free chlorine	none	none	160	0
Portland, OR	0.5	Soft	Chloramine	none	none	none	0
San Antonio, TX	17.5	Very hard	Free chlorine	none	none	26	0
San Diego, CA	14.0	Very hard	Chloramine	none	none	65	0
San Francisco, CA	3.6	Moderately hard	Chloramine	none	none	none	0
San Jose, CA	8.8	Hard	Chlorine and chloramine	none	6.2	10	1
Seattle, WA	1.5	Soft	Free chlorine	none	none	none	0
Tampa, FL	10.8	Very hard	Chloramine	4.6	6.9	none	0
Tucson, AZ	not published		Free chlorine	none	none	64	0
Washington, DC	8.1	Hard	Chloramine	none	none	none	0

Red: above EPA’s level. That’s 4 parts per trillion (ppt) for PFOA and PFOS. For lithium it’s 10 micrograms per liter (µg/L), a health reference level rather than a legal limit, which EPA compares at one significant digit, so up to 15 µg/L counts as at the level.
"None" means not detected. "High" is the highest single sample.
Sources: hardness from each utility’s published water quality data; PFAS and lithium from EPA’s national testing (UCMR 5), sampled mostly 2023 to 2025; violations from EPA’s federal drinking water database (SDWIS).

04 · Where the numbers come from

Read from the source, not repeated

PFAS and lithium readings come from EPA’s fifth Unregulated Contaminant Monitoring Rule, the agency’s national sampling of every large water system from 2023 to 2025. Violations and who buys water from whom come from EPA’s federal drinking water database.

Hardness isn’t in any reliable national file, so we read it from each utility’s own published data, usually its annual water quality report, and cite the document, the year and the day we read it. When a utility publishes a range, we show the range.

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