What water hardness level is considered high?
Water is considered hard above 7 grains per gallon (about 120 mg/L) and very hard above 10.5 grains per gallon (180 mg/L). Most of southeastern Pennsylvania's limestone country tests between 12 and 25 grains per gallon, which is firmly in the very hard range and is enough to scale a water heater within a few years.
The standard scale
Soft: 0–1 gpg (0–17 mg/L). Slightly hard: 1–3.5 gpg. Moderately hard: 3.5–7 gpg. Hard: 7–10.5 gpg. Very hard: over 10.5 gpg.
To convert: 1 grain per gallon = 17.1 mg/L (ppm) of calcium carbonate.
What high hardness actually does
Scale builds inside water heaters and pipes, cutting efficiency and shortening equipment life. A quarter-inch of scale in a water heater can raise the energy it uses noticeably.
Soap doesn't rinse. That's the film on shower doors, the stiffness in towels, and the dryness people blame on their skin rather than their water.
Fixtures, dishwashers and coffee makers clog and spot.
Why SE PA reads so high
Lancaster, Lebanon and the Chester Valley sit on carbonate limestone. Groundwater moving through it dissolves calcium and magnesium — the two minerals hardness measures. Homes on crystalline bedrock in Chester and northern Berks counties often read much softer but far more acidic instead.
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