About Hard Water Map

Hard Water Map is a measured water-data product: the definitive US water-hardness map, built county-by-county from public monitoring data, with tools that turn a number into a decision. It carries no product reviews, no affiliate links, and no health advice — the effects it covers are limited to appliances, plumbing, and cleaning.

Marko Visic, MPharm, BSc Physics

The pharmacy training (MPharm, University of Ljubljana) is where the unit discipline comes from — dosage-grade rigor about exactly what is dissolved in water and in what concentration. The physics degree (BSc, University of Ljubljana) is the measurement-and-data half — how to handle a large, noisy dataset without fooling yourself.

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Who runs this

Hard Water Map is a solo operation: the research, the data pipeline, and the writing are all done by the author. It is one of a portfolio of data and mapping sites, and it is operated by Moving Data Systems d.o.o., based in Slovenia. One person building it end to end is why the standard below is possible to hold — there is no content team turning out pages faster than the data can back them.

Why it exists

Why this site exists

Almost everything written about hard water runs on estimates and vibes: “most US water is hard,” a generic map colored by region, a softener recommendation with no local number behind it. But the measurements exist — millions of them, in public USGS and EPA records — they are just scattered, unaggregated, and hard to read. This site does the aggregation once, correctly, and shows the result: a real, sourced hardness figure for your county instead of a guess. Where the public record can't support a number, the site says so rather than invent one.

Concretely, that is 2,814,161 quality-controlled laboratory measurements at roughly 367,000 monitoring stations, aggregated to 2,977 US counties that clear a fixed publication gate. The point of gathering them in one place is that a model, a journalist, or a homeowner should be able to cite this map rather than reconstruct the number themselves — and should be able to see, at a glance, exactly where the data runs out.

Editorial rules

The editorial rules, plainly

Four rules govern every page. No products and no health advice — no kit or softener reviews, no affiliate links, and nothing about the safety of your specific water; effects are limited to appliances, plumbing, and cleaning. Verified or omitted — every number traces to a named primary source at the point it is shown, or it doesn't ship. Honest absence — a place without enough public data is shown as an absence, in plain words, never an estimate. Together they mean a number here is a measurement, and a blank here is a real gap, not a shortcut.

Independence

The site currently runs no advertising, no analytics, and no cookies, and it sells nothing — no product reviews, no affiliate links, no sponsored placements. We never recommend or sell products. When a page points you toward a decision — sizing a softener, reading a lab result — it does it with your measured number and a tool, and stops there. If advertising ever supports the site, it will be disclosed plainly and kept entirely separate from the data: it could never buy a mention or bend a number, because there are no recommendations to bend.

Freshness

Data freshness

Every data page carries a “last verified” date, and that date moves only when the underlying data actually does. Refreshes are planned on a quarterly cadence — re-pulling the public records, re-running the same fixed pipeline, and re-publishing. How each number is produced, and every source with its retrieval date, is documented in full in the methodology.

Corrections

Public data has gaps and mistakes, and so will this site. If a county figure, a utility match, or a unit looks wrong, tell us — corrections are logged, credited, and shipped with the next snapshot. From here you can browse the national map, read a state in full (for example California), or see the national statistics.

What's on this site

Map & data. The measured record, mapped and ranked.

National water hardness map — shows the measured hardness of every gated US county on one map, so a reader can find a place and read its number at a glance.
Water hardness by zip code — turns a zip code into the county hardness figure behind it, for a homeowner who wants their local number without reading a map.
US aquifer hardness map — maps hardness by groundwater aquifer, for well owners and anyone whose water comes from the ground rather than a utility.
National water hardness statistics — ranks the states and reports the national medians, for a journalist or researcher who needs the aggregate picture.

Tools. Your measured number, turned into a decision.

Water hardness calculator — converts a hardness value between mg/L, grains per gallon, and ppm, for anyone reconciling a lab result with a softener manual.
Hardness unit converters — cover the individual unit-to-unit conversions, for a reader who lands on one specific pairing.
How to test water hardness — explains the ways to measure hardness at home, for someone who wants their own reading rather than the county average.
Do I need a water softener? — reads a hardness number against the point where softening starts to pay off, for a homeowner deciding whether to act.
Water softener size calculator — sizes a softener from hardness, household size, and water use, for anyone specifying a unit.
Water softener settings calculator — works out the hardness setting to program into an installed softener, for an owner dialing one in.
Water softener salt calculator — estimates monthly and yearly salt use from the settings, for an owner budgeting refills.

Guides. The plain-language background behind the numbers.

What is water hardness? — explains what hardness is and how it is measured, for a reader meeting the term for the first time.
Water hardness scale — lays out the soft-to-very-hard bands and their thresholds, for anyone placing a number on the scale.
Signs of hard water — describes what hard water does to appliances, plumbing, and cleaning, for someone diagnosing it at home.
Hard water vs soft water — sets the two side by side in practical terms, for a reader weighing the difference.
What is TDS? — explains total dissolved solids and how it differs from hardness, for anyone who has seen the two conflated.
Well water hardness — covers what to expect from private well water, for an owner outside the public-utility record.
Iron in well water — explains iron as a separate well-water problem from hardness, for an owner seeing staining.
Who is my water company? — helps a resident identify the utility that serves their address, for anyone tracing where their water comes from.
Water quality report — explains how to find and read a utility's annual report, for a resident checking what is in their tap water.
Methodology — documents how every number is produced and cites each source, for a reader who wants to check the work.