💧 Water Quality & Plumbing Engineering
Water Hardness ($^\circ\text{dH} \leftrightarrow \text{ppm} \leftrightarrow \text{gpg}$) Converter
Convert mineral water hardness across $\text{mg/L CaCO}_3$ ($\text{ppm}$), German Degrees ($^\circ\text{dH}$), French Degrees ($^\circ\text{fH}$), Clark Degrees ($^\circ\text{e}$), and Grains per Gallon ($\text{gpg}$).
🏔️ Soft Mountain Stream (30 ppm)
🚰 Moderate Municipal Tap (100 ppm)
🛁 Hard Ground Well Water (220 ppm = 12.3 °dH)
🪨 Very Hard Limestone Aquifer (400 ppm = 22.4 °dH)
Input Water Hardness
German Degrees (°dH)
6.72 °dH
USGS Water Hardness Classification:
Moderately Hard Water (61 - 120 mg/L)
Grains / Gal (gpg)
7.01 gpg
French (°fH)
12.0 °fH
Clark (°e)
8.42 °e
💡 Hardness Equivalence:
$$1\text{ }^\circ\text{dH} = 17.848\text{ mg/L CaCO}_3 = 1.043\text{ gpg} = 1.785\text{ }^\circ\text{fH}$$
Understanding Water Hardness Measurement Standards
Water hardness is primarily caused by dissolved polyvalent mineral cations, mainly Calcium ($\text{Ca}^{2+}$) and Magnesium ($\text{Mg}^{2+}$):
- USGS Water Hardness Scale:
- Soft: $0 - 60\text{ mg/L}$ ($0 - 3.5\text{ gpg}$)
- Moderately Hard: $61 - 120\text{ mg/L}$ ($3.5 - 7.0\text{ gpg}$)
- Hard: $121 - 180\text{ mg/L}$ ($7.0 - 10.5\text{ gpg}$)
- Very Hard: $> 180\text{ mg/L}$ ($> 10.5\text{ gpg}$)
- Unit Definitions:
- $1\text{ }^\circ\text{dH}$ (German) $= 10\text{ mg/L CaO} = 17.848\text{ mg/L CaCO}_3$
- $1\text{ }^\circ\text{fH}$ (French) $= 10\text{ mg/L CaCO}_3$
- $1\text{ }^\circ\text{e}$ (English / Clark) $= 1\text{ grain CaCO}_3\text{ per Imperial Gallon} = 14.254\text{ mg/L}$
- $1\text{ gpg}$ (US Grain per Gallon) $= 1\text{ grain CaCO}_3\text{ per US Gallon} = 17.118\text{ mg/L}$