Choosing a Water Hardness Test Kit

Types of kit

Every kit on the market falls into one of a few formats. What changes is how the result is read and how fine the answer is. The full testing method, including how to take a sample, is in the hardness testing guide.

Kit formats at a glance

Quality Water Treatment's Pro Products 2403 is an example of the drop-count format. Its listing says the case holds Hardness #1, #2 and #3 reagents of 1 oz each, a square test bottle and a measuring tube. Quality Water Treatment sells this 2403 hardness field test kit (sold by Quality Water Treatment, our store) for reading hardness as a number at home, from $150 (October 2026). Replacement Hardness #3 reagent is a separate 1 oz purchase, from $7.95 (October 2026).

Accuracy and range

Nebraska Extension frames the trade-off simply: strips and home kits cost little and land close enough for an estimate, but it recommends a laboratory when accuracy counts. Penn State Extension adds that a third-party lab test is inexpensive and can stop you being oversold a system.

Three things affect how close any home kit gets:

1. Water temperature. Warm samples throw strip colors off, according to SoftPro, so draw from a cold tap.
2. How long the tap ran. The stores disagree here: SoftPro flushes about 30 seconds before dipping, Quality Water Treatment at least 5 minutes. Follow the kit's own directions and use the same routine every time.
3. Reading the scale. Strips sort the result into color bands, so the answer is a range. A drop kit gives a count you can convert directly.

Results convert at 17.1 mg/L (ppm) per grain per gallon. On the common scale, under 1 gpg is soft, 7 to 10.5 gpg is hard and over 10.5 gpg (180 mg/L) is very hard. A kit only needs enough range to place your water on that scale and give the softener a number; the settings guide explains where it goes. Pentair's 5600SXT manual accepts hardness settings from 1 to 199 gpg, so very hard well water still fits.

What a TDS meter can't tell you

A TDS meter reads total dissolved solids: everything dissolved in the water, not just calcium and magnesium. Montana State Extension explains why that makes it the wrong tool for a softener. Softening doesn't lower TDS; it exchanges calcium and magnesium for sodium or potassium, so the total stays about the same. A TDS reading therefore cannot tell you how hard your water is, and it cannot confirm a softener is working.

TDS meters are sold for checking reverse osmosis systems. For hardness, use a strip, a drop kit or a lab. If softened water seems hard, follow the checks in signs a softener is working rather than a TDS number.

Which kit to use when

Before buying or sizing a softener. Use a lab test or the most precise kit you can get, because the hardness figure sets the system size and salt use. Well owners who also need iron and other results can use a broader well-water kit. SoftPro sells a well water test kit (sold by SoftPro, our store) for homeowners checking a private well for common contaminants, from $159 (October 2026). City customers can start with the annual Consumer Confidence Report, as Nebraska Extension suggests.

When programming the valve. A drop-count kit gives the numeric gpg the hardness screen asks for. If you only have a mg/L figure, divide by 17.1 and round up, as SoftPro's Elite install guide advises.

For routine checks. Strips are enough to compare raw and softened water every few months. Treated water should read far below the raw sample; if the two come out close, look at the bypass, salt and settings.

When something seems wrong. Test raw and softened water with the same kit on the same day. If they match, see the troubleshooting guide or how to reset a softener.

Common questions

Related guides

• TestHow to test water hardness
• SettingsSoftener settings guide
• Water softener FAQ