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A water’s “hardness” is derived largely from contact with soil and rock formations. Hardness is a measure of the levels of metal ions, mainly calcium and magnesium in the form of carbonates, in water.  While it is not generally dangerous to safety or health, water with excessive hardness can cause problems with scale formation on fixtures that it comes in contact with.  Conversely, “soft” water can be corrosive, eroding pipe or other materials in which it comes in contact.   Some utilities adjust the hardness of water to achieve a level that will neither deposit scale, nor be too corrosive.

The Acton Water District is fortunate in that most of our wells have a moderate amount of hardness. We often receive questions about how many “grains” of hardness we have in our water.  Homeowners encounter this unit of measurement in manuals for dishwashers, fish tank filtering systems, etc.  It is a measurement not commonly used in the U.S, but can easily be calculated from mg/L, the unit commonly used to measure hardness.  Approximately 17 mg/L of hardness equals one grain per gallon.  Raw water hardness from our wells varies, but an average around 50 mg/L could be used as a “ballpark.”


50 mg/L in our water equates to 2.95 grains/gallon

Water from our wells falls into the “slightly hard” to “moderately hard” category.  Customers should be reassured that they will not experience the common problems attributed to very “hard” or very “soft” water.