How to Test Your Water for Hardness (At-Home Strip Test)

The fastest way to test your water for hardness is a test strip from Lowe's, Home Depot or Amazon: dip it, wait, and match the color to the chart on the bottle. Water at 7 grains per gallon (120 mg/L) or more is hard, and 7 is where I recommend a water softener; over 10.5 grains (180 mg/L) is very hard. A strip gives you a range. For an exact number, use a certified lab test or, on city water, your water supplier's yearly report.

Caller "My hardness is at 24. Is that, do I really, do I need the..."

Aidan "Milligrams per liter or grains per gallon?"

A well owner read me that in June. Whenever someone gives me a hardness number, I ask for the unit first, because 24 mg/L is soft water and 24 grains is very hard. This page is how to get your number and where it lands.

How to test hardness with a strip

A strip test takes under a minute: dip, wait, read. The one in my video is a hardness-only strip we bought on Amazon. If a softener is already in, a tap after it tests the softened water, not the water coming into the house.

1. Fill a clean glass

   Fill a clean glass with the water you want to test.

2. Dip the strip quickly

   Dip the colored end into the water and take it right out. WaterSafe's instructions say "Remove immediately," and Hach's total hardness method says to dip the strip "for 1 second."

   

3. Hold it level for 15 seconds

   Hold the strip flat and do not shake the water off. AquaChek's label says "Hold strip level for 15 seconds (do not shake excess water from strip.)" If your bottle gives a different time, use the bottle's.

4. Match the strip color to the chart

   Hold the strip next to the chart on the bottle and pick the closest color. Note the unit printed beside it, grains per gallon or ppm. The strip in my video matched the soft end of the chart, so that water needed nothing.

How accurate hardness strips are

A strip tells you if your water is hard, not the exact number. It is not a number to size a softener from. Hach's total hardness chart has six colors: 0, 1.5, 3, 7, 15 and 25 grains per gallon (0 to 425 ppm). Hach's own advice: "Test strips should not be used when an exact hardness value is required."

Callers run into that. One told me, "It's hard to tell on those test strips, but it was about, looked like around 400." Another had "extremely high hardness" on strips and wanted real numbers for iron, pH and hardness; I told him the most accurate way is a lab. A buyer who reported his hardness from a strip added, "Test strip testing, so close but not lab values."

They're fairly accurate for what they are. If the strip says soft, you are done. If it says hard, get the number before you buy anything.

Grains per gallon or mg/L

To get grains per gallon, divide mg/L by 17.1. Ppm and mg/L are the same thing. Softeners are sized in grains, and our lab reports give hardness both in ppm and in grains per gallon, so the same water can read 210 on one line and 12.3 on the next.

A caller once told me "really hard water too, like 40," and another "my hardness is a 12.9." In both cases my first question was which unit. 40 mg/L is soft; 40 grains is very hard.

Some strips read in German degrees (°dH). One German degree is 17.8 ppm.

Water hardness scale

The USGS calls water over 7 grains (120 mg/L) hard and over 10.5 grains (180 mg/L) very hard. The bands are the USGS's; the grains and the last column are mine.

The Water Quality Association splits the soft end finer: under 1 grain is soft and 1 to 3.5 is slightly hard. That is why a lab report can call 2.5 grains "slightly hard." Above 3.5 the two scales agree.

Almost half of the well tests my customers sent in since May came back at 7 grains or more, and one in three over 10.5. The highest was 1,760 mg/L, about 103 grains. The hardest I've seen treated was 105 grains, a customer of ours in Kansas.

How to get an exact hardness number

A certified lab gives you the exact number. On city water, your supplier's yearly report may already have it.

On a well, our well water test kit ($199) goes to an ISO/IEC 17025 accredited lab and reports 53 contaminants and water-chemistry values, hardness in ppm with the grains per gallon worked out. Results usually take 2 to 4 weeks from the order. If hardness, iron and pH are all you want, a local lab will be faster and probably less expensive, and I tell callers that too. Best water hardness test kit compares the strips and lab tests side by side.

On city water, your water bill doesn't show it. Community water systems must send customers a Consumer Confidence Report, also called an annual drinking water quality report, each year by July 1; the EPA's CCR page shows how to find yours. On my video I call it a VOC report; the name to ask for is the Consumer Confidence Report. Hardness is not a regulated contaminant, so not every report lists it; if yours doesn't, call your supplier and ask. The lab tests on those reports are accurate. For a wider check of city water, the city water test kit is $199.

What to do with your number

Under 7 grains you don't need a softener; at 7 and above I recommend one. A caller read me "Calculated hardness, 42 PPM or 2.5 per gallon," and I told her she was fine, as long as it's below 7. Penn State Extension puts it the same way: below 7 grains "will probably not cause major scaling and soap film."

Tankless water heaters put a hardness limit in the manual. I checked five makers:

The biggest mistake I see is people who test, find hard water, and ignore it. Then they have scale in the plumbing and are replacing water heaters, dishwashers and washing machines.

The softener size comes from your hardness and how many people live in the house; the water softener size calculator works it out. If your pH is low, an acid neutralizer goes in too, and I set its place from your test. The neutralizer adds hardness, and the water softener sizing guide covers what that does to the size.

You have your hardness number

Send me your hardness number

Text a photo of your report to 443-277-2204 and Aidan will read it for you, free. Tell me how many people live in the house.

Text Aidan443-277-2204 Call800-460-5810Aidan

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