About this site and our method

Last updated: 2026-10-28

HardnessReport answers one question per city: how hard is the tap water, according to the utility that supplies it? We copy each hardness number as stated from the utility's own dated report. We convert at 17.1 mg/L per grain and use the USGS scale for the class.

The rules we follow

Primary sources only. Each number comes from the utility's own report or data page. We open the document itself. We do not copy from other lookup sites or search snippets.
Stated as published. We give the average and range the utility gives, in its units, with the report year. If the utility gives no average, range or year, we say so.
Our math is labeled. Where we convert units, we show the arithmetic: mg/L ÷ 17.1 = gpg.
Dated. Every page shows a “Last updated” date. City and state pages also show the date we last checked the utility's documents. Utilities publish new reports each year, usually by July 1.
Utility, not ZIP code. A ZIP code can be split between water systems. We publish by utility and name the system.
Scope. We cover hardness only, not health or safety. For those, read your utility's full report.
Disagreements are noted. If other sites show a different number, we say so and explain likely reasons, without guessing at motives.

The hardness scale we use

We use the USGS scale.

USGS hardness classes in mg/L and grains per gallon
Class (USGS)	mg/L (ppm) as CaCO₃	Grains per gallon (÷ 17.1)
Soft	0–60	0–3.5
Moderately hard	61–120	3.6–7.0
Hard	121–180	7.1–10.5
Very hard	more than 180	more than 10.5

Class limits: USGS Water Science School, “Hardness of Water”. Grain values are our conversion at 1 gpg = 17.1 mg/L, rounded to 0.1.

The limits of these numbers

A system-wide average is not a reading at your tap. Hardness changes with season, source and plant. Buildings with their own softeners will differ. For your own number, use a home test kit or ask your utility.

How we handle corrections

When a utility publishes a new figure, we update the page and show the new year.

If you report an error and we confirm it, we fix it promptly and add a dated line to the update log below.

How to report an error

To report an error or ask a question, email contact@hardnessreport.com.

Update log

2026-10-27: Added the privacy and terms pages, breadcrumbs and this log. Headings now read as statements. The privacy page names Cloudflare Web Analytics.
2026-10-26: Checked the Austin, Houston, Las Vegas, Phoenix and San Antonio figures against each utility's own documents.