How to Test Water Hardness

If you've noticed limescale on your faucets, spots on your dishes, or soap that won't lather properly, hard water is the likely culprit. But knowing you probably have hard water and knowing exactly how hard your water is are two different things, and that number matters when you're deciding what to do about it.

Here's how to test your water hardness, what the results mean, and what Phoenix-area homeowners typically find when they check.

Key Takeaways:

• Water hardness is measured in grains per gallon (gpg). Anything above 10.5 gpg is classified as very hard.

• Mesa, Scottsdale, Chandler, and Gilbert water typically runs 12-18 gpg, well into the very hard range.

• DIY test strips ($8-$15) are an easy, accurate-enough starting point for most homeowners.

• Liquid titration kits and lab tests offer more precision for sizing water treatment systems.

• A free professional assessment gives you the most complete picture of your water quality and treatment options.

The Water Hardness Scale

Water hardness is measured in grains per gallon (gpg): the concentration of dissolved calcium and magnesium minerals in your water. Some labs and test kits also use parts per million (ppm) or milligrams per liter (mg/L), which are equivalent to each other.

Here's how the scale breaks down:

ClassificationGrains per Gallon (gpg)Parts per Million (ppm)Soft0 - 10 - 17Slightly Hard1 - 3.517 - 60Moderately Hard3.5 - 760 - 120Hard7 - 10.5120 - 180Very Hard10.5+180+

Most municipal water in the U.S. falls somewhere in the moderately hard to hard range. Phoenix-area water is a different story.

Water Hardness in the Phoenix Metro Area

The Valley is well-known for having some of the hardest municipal water in the country. Here's what homeowners in different cities typically see:

CityTypical Hardness (gpg)ClassificationMesa16 - 18 gpgVery HardScottsdale12 - 16 gpgVery HardChandler14 - 18 gpgVery HardGilbert15 - 18 gpgVery HardTempe13 - 16 gpgVery HardPhoenix (City)12 - 16 gpgVery Hard

These figures come from municipal water quality reports and can shift slightly depending on the time of year and the source water mix your city is drawing from (Salt River Project vs. groundwater). But the bottom line for every city listed above: you almost certainly have very hard water.

For comparison, the national average is around 7-8 gpg. Valley homeowners are typically dealing with water that's two to three times harder than average.

How to Test Your Water Hardness

There are several ways to find out your exact hardness level, ranging from free to a few dollars to a professional assessment.

Option 1: Check Your City's Water Quality Report

Every municipal water provider is required to publish an annual water quality report (also called a Consumer Confidence Report). These reports include hardness data and are usually available on your city's website.

This is the easiest starting point and costs nothing. The limitation: it reflects the water leaving the treatment plant, not necessarily what comes out of your tap, older pipes and home plumbing can affect mineral content.

Option 2: DIY Test Strips

Water hardness test strips are inexpensive, widely available, and easy to use.

Where to buy: Home improvement stores (Home Depot, Lowe's), Amazon, or pool supply stores. A pack of 50-100 strips typically runs $8-$15.

How to use them:

1. Fill a clean glass with cold water from your tap.

2. Dip a test strip into the water for the time specified on the package (usually a few seconds).

3. Remove the strip and wait 30-60 seconds for the color to develop.

4. Compare the color to the chart on the packaging.

5. Match the color to a hardness value in gpg or ppm.

Test strips are accurate enough for most homeowners' purposes. They'll confirm whether you're in the soft, moderate, or very hard range, which is usually all you need to make decisions about water treatment.

Tip: Test in the morning before much water has been used, and run the tap for 30 seconds first to clear any standing water from the pipes.

Option 3: Liquid Titration Test Kits

These kits are a step up in accuracy from test strips. You add drops of a reagent solution to a water sample until the color changes, then count the drops to calculate hardness.

Where to buy: Pool supply stores or online. Kits typically run $10-$25.

They take a few more minutes than test strips but give a more precise reading, useful if you're sizing a water softener and need an accurate number to work with.

Option 4: Lab Testing

For the most comprehensive picture of your water quality, not just hardness, but pH, iron content, chlorine, and other factors, you can send a water sample to a certified lab. Costs range from $30-$100 depending on what's included in the panel.

This is worth considering if you're on well water, have older pipes, or want a complete picture before investing in a water treatment system.

Option 5: Professional In-Home Assessment

A plumber or water treatment professional can test your water on-site and walk you through the results. This is the most thorough option, and it comes with the added benefit of having someone who can explain what the numbers mean for your specific home and plumbing setup.

What to Do With Your Results

Once you know your hardness level, here's how to think about next steps:

• Under 7 gpg: Your water is in the moderate range. You may notice some scaling over time, but it's manageable. A point-of-use filter may be sufficient.

• 7-10.5 gpg: You're in the hard range. Scaling will build up on fixtures and inside appliances. A water softener is worth considering, especially if you have a newer water heater or appliances you want to protect.

• 10.5+ gpg: Very hard water. At this level, untreated water will noticeably shorten appliance lifespans, reduce water heater efficiency, and cause regular scaling. A whole-home water softener is the most practical solution for long-term protection.

If you're in Mesa, Scottsdale, Gilbert, or anywhere else in the Phoenix metro area, there's a strong chance you're in that last category.

Ready to Know Your Exact Number?

A test strip gives you a ballpark. A professional assessment gives you the full picture, including what's happening inside your pipes and whether your home's plumbing is a good fit for a water softener or other treatment options.

Superstition Plumbing offers free in-home water assessments for Phoenix-area homeowners. We'll test your water, walk you through the results, and give you honest recommendations, no pressure, no overselling.