Finding Your Tap Water Hardness From a Utility Report

Your water supplier is the first stop, and it costs nothing. The USGS says information about hardness at a home or immediate locale should be provided by the local health agency or local water utility.¹

The annual report (United States)

In the US, community water systems must deliver a Consumer Confidence Report to customers. The EPA also calls it an annual drinking water quality report.² Suppliers must send it each year by July 1.²

Lost yours? There are two routes. You can call your local water supplier, or use the EPA's online search tool to get a copy.²

What may be missing

Read the EPA's list of what a report contains. It covers the water source, contaminants found, and phone numbers for more information.² Hardness isn't named in that list. So the report may or may not include a hardness figure.

That's not a dead end. Scan the table of water results for a line called hardness, total hardness or calcium carbonate. If nothing's there, use the phone number printed on the report and ask the supplier for the typical hardness of your area's water.

Water hardness varies throughout the United States.¹ A supplier may serve several zones, so give them your street address, not just your city.

Reading the number

Check the unit first. Penn State says a report will use one or both of two units, ppm or mg/L and grains per gallon.³ A gpg equals approximately 17 mg/L or ppm.³ The units page has the full table.

Then match the value to your machine's scale. Makers phrase theirs in different ways, and the maker's own guidance is the one to match against.

Keep a short note of the figure, the unit and the date you found it. You'll want all three later if you compare it with a home test, or if you change to filtered or bottled water. A figure without a unit is almost useless, because a number that looks high in one unit can look small in another.

Outside the United States

The EPA report is a US rule. This page doesn't cover how other countries publish their data. In Australia, the UK, Canada and elsewhere, the usual starting point is still your own water supplier. Look on its website for a water quality or hardness page, or ring customer service and ask. Ask for the answer in a named unit so you can convert it.

Things to keep in mind

• Reports are annual, so check the date on yours.
• If you use a household softener, the water at the kitchen tap may not match the supplier's figure.
• A well or private supply isn't covered by the supplier's report.

For any of those situations, a home test is the next step. Taking one at home is covered next.