You’ll see water hardness measured in two units: PPM (parts per million) and GPG (grains per gallon). One GPG equals 17.1 PPM. If your water reads 180 PPM, that’s roughly 10.5 GPG. Anything over 7 GPG (120 PPM) is considered hard and will start forming that film I was yelling about earlier. Most water softeners are set to remove down to 1 GPG, which is basically rain water.
Between you and me, I don’t even think about PPM. I just memorize the GPG scale because it makes me feel like a whiskey distiller talking about “grains.” But use whatever unit makes you feel smarter.
How To Measure Water Hardness At Home at Ava Lazarev blog
When to Call in the Professionals
If your test strips show over 180 PPM (10.5 GPG), you don’t need a test—you need a water softener. At that level, your water heater is accumulating a layer of scale that’s costing you 20-30% more energy to heat water. That’s like burning money to watch your faucets turn white.
Also, if you notice blue-green stains on your sinks (that’s copper eating through your pipes from acidic water), or orange stains (iron), a simple hardness test won’t cut it. Those are different problems. Hardness is calcium and magnesium—the friendly, white-scum minerals. Stains of other colors mean you need a full water panel, not just a strip.
