How to find your tap water hardness

The most dependable number comes from whoever supplies your water. Hardness varies from place to place, so a national figure or a neighbor's guess won't do the job.

Start with the water supplier

USGS says information that's directly relevant to hardness at a home should come from the local health agency or local water utility¹. It also warns that its own older national hardness data weren't designed for local decisions¹.

In the United States, community water systems have to send customers a Consumer Confidence Report each year². EPA describes it as an annual drinking water quality report that gives information about local drinking water quality². Reports must go out by July 1 each year².

Missed yours? You can call your local water supplier, or use EPA's online search tool to find the report². EPA's list of what a report contains covers the water source, contaminants found and similar items. Hardness isn't on that list, so a report may not show it².

If it's missing, ask the supplier. Say you want the hardness, and ask for the unit too. The page on what hardness means shows why the unit matters.

That Consumer Confidence Report is a United States rule. Canada, the UK and Australia have their own systems, so look at your own supplier's website or phone line.

Why a neighbor's number may not match yours

Hardness depends on where the water comes from. Wikipedia notes that areas with complex geology can produce water with varying degrees of hardness over short distances³.

Here's how far cities can differ. Wikipedia lists Melbourne, Australia at 10–26 ppm total hardness as calcium carbonate and Adelaide at 134–148 ppm³.

Test strips and meters

Some machines come with a strip. Breville says that if your machine includes a water hardness test strip, you should test the water you'll be using⁴. It adds that you should set the machine's hardness level to match, following the instructions for your model⁴.

Changed your water source? Breville says to retest and update the setting where the machine has one⁴.

A TDS meter is a different tool. It's a digital meter⁵. It estimates dissolved solids from conductivity, and Wikipedia says that gives an approximate value⁵. It isn't a hardness reading.

What to write down

Keep three things together:

• The number.
• The unit (ppm, mg/L, grains per gallon, or degrees).
• The date and where it came from.

Reports are yearly, so one can go out of date. Check again if you start using filtered or bottled water.

If you don't get water from a supplier

EPA's report rule applies to community water systems². If your water doesn't come from one, there may be no report to ask for. USGS names the local health agency and local water utility as sources of local hardness information¹. This site doesn't sell tests or point to any seller.