What hard water is
Hardness comes mainly from calcium and magnesium dissolved in water, according to the U.S. Geological Survey. The USGS calls water over 180 mg/L "very hard." One grain per gallon equals 17.1 mg/L, so that line is about 10.5 grains per gallon.
What the local numbers say
| Apache Junction | Hard: greater than 10.5 grains per gallon |
|---|---|
| Mesa | 12 to 22 grains per gallon |
| Chandler | 10.1 to 16.8 grains per gallon |
| Queen Creek | 6 to 17 grains per gallon |
| Scottsdale | 16 to 25 grains per gallon, by area |
From each city, town or water district: Apache Junction, Mesa, Chandler, Queen Creek, Scottsdale.
Where the water on your glass comes from
Sprinklers that reach the house, a hose used to rinse off dust, and misting systems all put tap water on glass. In the sun it dries quickly and leaves its minerals where it was. If your spots line up with a sprinkler head, you have found the source.
What you can do
Aim sprinklers away from glass, and do not rinse windows with a hose and let them air dry. For spots already there, point them out at your free quote and ask Robert what he can do for that glass.