The Well Water Lab Hardness Band Table

The Hardness Band Table is a short table that The Well Water Lab uses to name the four hardness bands published by the U.S. Geological Survey. Hardness is reported in milligrams per liter as calcium carbonate, and the table turns a number from a laboratory report into a plain word. It is a reading aid for a result you already have.

What it is

Hardness describes the amount of dissolved calcium and magnesium in water. A laboratory reports it as a number, and the table places that number in one of four bands. The bands are the same ones the U.S. Geological Survey uses, and the table repeats them without adding to or changing them.

The levels

• Soft: 0 to 60 milligrams per liter as calcium carbonate.
• Moderately hard: 61 to 120 milligrams per liter.
• Hard: 121 to 180 milligrams per liter.
• Very hard: above 180 milligrams per liter.

How to use it

Find the hardness result on your laboratory report. Check the unit, which must be milligrams per liter as calcium carbonate, or convert it first. Find the band that contains the number and write the band next to it. Some reports give grains per gallon, and those values must be converted before the table is used.

Write the band beside the result on your copy of the report. Note the laboratory name on the same page. Use the same unit every time you compare results.

Limits

The table names a band for a number. It does not say whether a given hardness is a problem for a household, and it does not choose equipment. Those decisions depend on the household and on the full laboratory report. A result near the edge of a band should be read with care, since laboratory results carry some uncertainty.