Best Water Hardness Test Kits (2026): Know Your Number Before You Buy a Filter

I started recommending Varify after seeing it consistently outperform cheaper alternatives in independent testing. What matters in test strips isn't the number of strips in the bottle — it's whether the color change is distinct enough to actually read accurately. Varify's color blocks are well-separated, which is more important than it sounds when you're trying to distinguish between 150 ppm and 200 ppm in mediocre kitchen lighting.

The strips test specifically for calcium and magnesium — the two minerals responsible for hard water buildup. You dip a strip for about a second, shake off the excess, and compare it to the color chart after 15 seconds. The color stays stable long enough to read accurately, which is a common failure point with cheaper strips that keep shifting after the read window closes.

What I like is the GPG markings on the chart alongside the ppm values — if you're cross-referencing against TapWater.org city data (which uses GPG), you don't have to do any conversion math. 150 strips is also genuinely more than you need for a household, which means you can test multiple faucets, your shower, and your water softener output without burning through the pack.

The DIPSTIK kit is straightforward: 150 hardness-only strips, same 15-second read window, same ppm range as the Varify. The color chart is slightly less detailed — fewer intermediate color blocks — which means your reading will land in a wider range (e.g., "somewhere between 150–250 ppm" rather than a tighter estimate).

For most renters or anyone who just wants to confirm whether their water is hard before deciding whether to buy a shower filter, that's fine. You don't need lab precision to know that 300 ppm water is going to scale your coffee maker. Where the DIPSTIK falls slightly short is at mid-range hardness levels where the distinction between "moderately hard" and "hard" matters for filter selection — at that point, the Varify's better color separation is worth the extra $3.

The Hach 5-B is a different category of product entirely. Instead of dipping a strip, you use drop-count titration: you add reagent drops to a measured water sample until a color change occurs, then count the drops. Each drop corresponds to a precise ppm value. It's the same methodology municipal water labs use — not as fast as strips, but significantly more accurate, particularly at low hardness levels where strip color differences become unreliable.

I'd point someone toward the Hach kit in three scenarios: you just installed a water softener and need to verify the output is below 50 ppm; you have well water and want reliable baseline data before making any treatment decisions; or your tap hardness is high enough that you're evaluating expensive whole-house systems and want an exact number before spending $1,000+.

The 5-B is not the product for quick spot-checks. The reagents have a shelf life, the process takes a few minutes, and there's a small learning curve on the first use. But for what it is — a professional-grade hardness test you can run at home — $35 is genuinely inexpensive.