How to Test Water Hardness

Three ways to test

Hardness is the calcium and magnesium dissolved in your water. It is reported in grains per gallon (gpg) or in milligrams per liter (mg/L), which is the same as parts per million (ppm). You need the number for two jobs: deciding whether to soften at all, and programming the softener's hardness setting. The settings guide shows where that number goes.

1. Test strips. A paper strip changes color in the sample and you match it to a chart. Nebraska Extension says home test kits and dip strips are inexpensive and give a good estimate.
2. Drop-count (titration) kits. You add reagent to a measured sample and count drops until the color changes, so the result comes out as a number rather than a color band.
3. Laboratory test. Nebraska Extension recommends a lab test for accuracy. Penn State Extension suggests having water tested by a third-party lab, noting it is inexpensive and helps you avoid being oversold equipment.

If you are on city water, check the Consumer Confidence Report first. Nebraska Extension points city users to this annual report, which lists hardness for your supply. Private well owners have no such report and need to test.

For strips, the two owned-store guides give slightly different timing. SoftPro's method: let the tap run roughly 30 seconds, hold the strip in the sample 3 seconds, then read it against the chart after 20-30 seconds. Quality Water Treatment says to run the tap for at least 5 minutes and dip for 3 to 5 seconds. Follow the directions printed with your strips. SoftPro also notes that hot water skews strip results, so take every sample from a cold tap.

Using a drop-count kit

A drop-count kit takes a few minutes longer than a strip but gives a count you can read directly. Take the Pro Products 2403 as an example. Its store listing describes a plastic carry case holding Hardness #1, #2 and #3 reagents (1 oz each) plus a square sample bottle and a graduated tube.

The sample size, reagent order and how drops convert to grains differ between kits, and the 2403's store listing covers contents rather than method, so follow the instruction card in the box. Some general habits still apply:

1. Use cold water. As with strips, a cold sample avoids skewed readings; run the tap first so the water comes from the main, not the pipe.
2. Fill to the mark. The drop count only means something if the sample volume matches the card.
3. Keep a log. Note the count, the date and which tap you used, so later tests compare like with like.
4. Restock reagents. Quality Water Treatment sells Hardness #3 solution in 1 oz bottles for the 2401 and 2403 kits, from $7.95 (October 2026).

If you want the complete case, the Pro Products 2403 water hardness field test kit (sold by Quality Water Treatment, our store) is sold by Quality Water Treatment for home hardness testing, from $150 (October 2026). Kit types are compared in choosing a water hardness test kit.

Reading the result

Lab reports often give mg/L. Dividing that figure by 17.1 converts it to gpg, and SoftPro's Elite install guide rounds the answer up before it goes into the valve. Montana State Extension notes that 1 gpg equals 17.1 mg/L expressed as calcium carbonate, and that ppm and mg/L are the same unit.

Virginia Tech says hardness under 7 gpg (120 mg/L) generally doesn't need treatment. Montana State uses a different scale, with 121 to 300 mg/L called hard and over 300 called very hard, so a "hard" label from one source may not match another. Go by the number, not the label.

Iron changes the setting. Clear-water (ferrous) iron uses up resin capacity too, so follow your softener's manual for how to allow for it. SoftPro's Elite guide, for its own valve with no iron filter, adds 3 gpg to the hardness setting for iron of 2 to 3 ppm. Oxidized iron, iron bacteria and higher iron need a dedicated iron filter ahead of the softener.

Once you have the number, the regeneration frequency guide shows how it combines with water use to set the interval.

Testing softened water

The same test tells you whether a softener is doing its job. SoftPro's method is to test raw and softened water side by side: a wide gap between the two means the softener is working, while two readings that are almost the same suggest water is bypassing the resin or regeneration has stopped.

1. Find a raw-water tap. An outside spigot or a line that leaves the main before the softener usually carries hard water.
2. Sample a cold softened tap inside the house, after running it.
3. Test both with the same kit within a few minutes of each other.
4. Compare. If softened water reads close to the raw sample, check the bypass position, the salt level and the hardness setting before anything else, as both Quality Water Treatment and the Fleck service manual (42684 Rev B) list those as simple causes.

Watch the salt as well: SoftPro expects the level to fall over the weeks, and a tank that never goes down while the taps run hard suggests regeneration isn't happening. A TDS meter cannot do this check, because softening swaps one dissolved mineral for another rather than removing them. The how to tell if a softener is working guide and the troubleshooting guide take it from there.

Common questions

Related guides

• SettingsWater softener settings
• TestChoosing a hardness test kit
• FixIs your softener working?

Parts for this job

Pro Products Water Hardness Field Test Kit

Check current options and prices at Quality Water Treatment.

View at Quality Water Treatment

watersoftenerguide.net is owned by the team behind SoftPro Water Systems and Quality Water Treatment, which sell some of the parts and systems we link to. Ownership disclosure