Hardness by State Hardest Cities Hardness Scale Softener Guide About & Method

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District of Columbia Water Hardness

1 cities ranked by hardness.

Washington

6.8 GPG · 117 ppm

Water hardness by US & Canadian city — GPG, ppm, source, and what to do about it.

Data sourced from USGS, EWG, and municipal annual water quality reports.

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