Best Water Hardness Test Kits: Strips, Drop Kits, and Why a TDS Meter Isn’t One
Quick answer: for most homes, Varify hardness test strips (0–25 gpg) are the easiest way to test water hardness. For very hard well water, ITS WaterWorks strips read up to 1,000 ppm. To check that a softener is working, use a drop-count kit like the Hach HA-71A, which reads in 1 mg/L steps. A TDS meter can’t measure hardness: it estimates all dissolved minerals together, and a softener barely changes that number. On city water, your utility’s annual water quality report may list hardness for free.
Our picks:
- Best test strips: Varify Water Hardness Test Kit (0–25 gpg, 150 strips)
- Best for very hard water: Industrial Test Systems WaterWorks Total Hardness (0–1,000 ppm)
- Most precise: Hach HA-71A drop-count kit (1 mg/L steps)
- Best TDS meter (not for hardness): HM Digital TDS-3
- Free for city water: your utility’s water quality report
How we chose: we haven’t used these kits ourselves. We compared their ranges and steps from the makers’ pages and sellers’ listings, and say which is which.
How hard is your water? The USGS scale
Hardness is measured as calcium carbonate, in mg/L (the same as ppm) or grains per gallon (gpg). One grain per gallon is 17.1 mg/L. Hach notes that hardness is caused almost entirely by calcium and magnesium. The U.S. Geological Survey groups it like this:
| USGS class | mg/L (ppm) | About gpg |
|---|---|---|
| Soft | 60 or less | 3.5 or less |
| Moderately hard | 61–120 | 3.6–7 |
| Hard | 121–180 | 7.1–10.5 |
| Very hard | More than 180 | More than 10.5 |
Softened water is a different target: North Dakota State University Extension counts water under 1 gpg (17 mg/L) as soft. That’s why checking a softener needs a test that reads small amounts.
Which hardness test do you need?
Pick your goal, and add a reading if you already have one. You’ll get the test that fits and what your number means.
Best test: ITS WaterWorks Total Hardness strips
They read from 0 to 1,000 ppm (about 58 gpg), so they cover any water. Once you know roughly where you are, Varify strips read finer steps up to 25 gpg. See the ITS strips.
- Test the untreated water: an outside tap or the softener in bypass. Our hardness settings guide shows how to enter the number.
- On city water, check your utility’s annual water quality report first: it may list hardness for free.
Classes follow the USGS scale, and the softener setting follows the iron rule in Whirlpool’s and Rheem’s manuals. Your softener’s manual comes first.
Compare hardness tests
| Test | Type | Range | Smallest step | Best for |
|---|---|---|---|---|
| Varify Water Hardness Test Kit | Test strips (150) | 0–25 gpg, 0–425 ppm | Color steps on the chart | Setting a softener; testing often |
| ITS WaterWorks Total Hardness | Test strips (50) | 0–1,000 ppm | 40 ppm at the low end (0, 40, 80, 120…) | Very hard or unknown water |
| Hach HA-71A | Drop-count kit (about 100 tests) | 1–20 mg/L and 1–20 gpg | 1 mg/L or 1 gpg per drop | Checking softened water |
| HM Digital TDS-3 | TDS meter | 0–9,990 ppm TDS | 1 ppm (below 1,000) | Not hardness; checking RO water |
| Utility water quality report | Annual report | Whatever the utility lists | — | A free first look on city water |
Our picks
Varify Water Hardness Test Kit
A dip-and-read strip kit with enough strips to test your untreated and softened water many times. Its color chart reads in both gpg and ppm, so there’s no conversion to do before you set a softener.
- Range: 0–25 gpg and 0–425 ppm
- Strips: 150: 100 in a bottle plus two separately sealed pouches
- Result: in seconds, read against a color chart
Good to know: these details come from the seller’s listing. The chart tops out at 25 gpg, so if your strip matches the top color, switch to the ITS strips below to find out how hard the water really is.
Check price on AmazonIndustrial Test Systems WaterWorks Total Hardness Strips
Industrial Test Systems is a U.S. maker of test strips. These cover a much wider range than most hardness strips, so they work on very hard well water, or as a first test when you have no idea how hard your water is.
- Color steps: 0, 40, 80, 120, 180, 250, 425 and 1,000 ppm (ITS lists the same steps)
- Strips: 50 per bottle; the listing calls it a 3-second test
Good to know: the steps are wide, especially at the top, where a reading between 425 and 1,000 ppm is an estimate. The lowest step above zero is 40 ppm (about 2.3 gpg), so these strips can’t confirm softened water is under 1 gpg.
Check price on AmazonHach HA-71A Total Hardness Test Kit
A drop-count titration kit from Hach, a lab equipment maker. You add a reagent one drop at a time and count the drops until the sample changes color, which gives an actual number instead of a color match.
- Ranges: 1–20 mg/L, where each drop equals 1 mg/L, and 1–20 gpg
- Tests: about 100, with reagents and equipment in a carrying case
- Why it helps: the low range can confirm softened water is under 17 mg/L (1 gpg)
Good to know: it wasn’t on Amazon when we checked, so this button goes to Hach, which lists the price on request. Its high range tops out at 20 gpg, so pair it with the ITS strips for very hard water. Hach marks some reagents as possibly hazardous to ship.
See it at HachHM Digital TDS-3
A pocket meter that reads total dissolved solids in seconds. It’s useful for checking a reverse osmosis system or comparing two water sources. Read why it can’t measure hardness before you buy one for a softener.
- Range: 0–9,990 ppm, in 1 ppm steps up to 999 and 10 ppm steps above that
- Accuracy: ±2% from 0 to 5,000 ppm
- Temperature compensation: automatic, from 1 to 50°C (33–122°F)
- Conversion: uses a factor of 0.5, based on sodium chloride
Good to know: these specs come from HM Digital’s own page. For more on RO, see water softener vs reverse osmosis.
Check price on AmazonYour utility’s water quality report
Community water systems publish a yearly water quality report, which the EPA calls a Consumer Confidence Report. You can find yours with the EPA’s search tool or by calling your water supplier. Some reports include hardness, so it’s worth a look before you buy anything.
- Best for: a free first number on city water
- Limits: it covers the whole water system, not your tap, and not every report lists hardness
Good to know: on a private well there’s no report, so test the water yourself. Our well water test kit guide covers lab tests that include hardness and iron.
Find your report (EPA)Can a TDS meter test water hardness?
No. NDSU Extension explains that an EC/TDS meter measures how well the water conducts electricity, then multiplies that by a conversion factor to estimate total dissolved solids. That gives one number for everything dissolved in the water, with no breakdown of which minerals are there. Hardness is just the calcium and magnesium part, so the same TDS reading can come from hard water or from water full of sodium.
That’s also why a TDS meter can’t tell you whether a softener is working. A softener swaps calcium and magnesium for sodium (see how a water softener works), so the minerals change but the total dissolved in the water stays about the same. Use a hardness test on the softened water instead.
How to test water hardness at home
- Test the untreated water for the setting: an outside tap (Rheem’s manual recommends leaving outside faucets on hard water) or the softener in bypass.
- Follow the kit’s timing exactly. Strips are read against the chart within a set time; drop kits count drops until the color changes.
- Test softened water from a cold tap after the softener to check it’s working.
- Write down the number and unit. Most softeners want gpg; divide mg/L by 17.1 to convert.
Then enter it in our hardness setting guide, or use the size calculator if you’re buying a softener.
Frequently asked questions
What is a normal water hardness level?
The USGS calls water soft at 60 mg/L (about 3.5 gpg) or less, moderately hard at 61–120 mg/L, hard at 121–180 mg/L and very hard above 180 mg/L.
Are water hardness test strips accurate?
They’re accurate enough to set a softener, but they read in color steps, not exact numbers. The ITS strips, for example, jump from 0 to 40 to 80 ppm. For an exact number, or to check softened water, use a drop-count kit.
Does a TDS meter measure hardness?
No. It estimates all dissolved solids from electrical conductivity, so it can’t separate calcium and magnesium from other minerals like sodium.
How do I check my water hardness for free?
On city water, look up your utility’s annual water quality report through the EPA’s search tool, or call the utility. Not every report lists hardness, and it covers the whole system, not your tap.
What hardness should softened water have?
Under 1 gpg (17 mg/L), which NDSU Extension counts as soft. If softened water tests higher, see our softener checker.
Related guides
- Water softener hardness settings
- Best well water test kits
- What size water softener do you need?
- Water softener benefits: is a softener worth it?
Sources
- U.S. Geological Survey, Water-Resources Investigations Report 02-4045, Table 3 (hardness classes).
- NDSU Extension, Using Electrical Conductivity and Total Dissolved Solids Meters to Field Test Water Quality (WQ1923, revised January 2025).
- Hach, Total Hardness Test Kit, Model HA-71A.
- HM Digital, TDS-3 specifications.
- Industrial Test Systems, WaterWorks Total Hardness.
- U.S. EPA, Consumer Confidence Reports.