What concentration of hardness is considered hard or soft?

Document ID

Document ID TE3427

Published Date

Published Date 27/05/2017
Question
What concentration of hardness is considered hard or soft?
Summary
Concentration of hardness considered hard or soft.
Answer
There is no universal agreement on what exact concentrations are considered hard or soft. The following information was taken from the U.S. Department of Interior and Water Quality Association. Other organizations may use slightly different classifications:
 
Classification mg/L gpg (grains per gallon)
Soft 0 - 17 0 - 1
Slightly hard 17 - 60 1 - 3.5
Moderately hard 60 - 120 3.5 - 7.0
Hard 120 - 180 7.0 - 10.5
Very Hard >180 >10.5