Question

A groundwater is being considered for use as a domestic supply. The water has a temperature of 15

Answer 1

The hardness of your water will be reported in grains per gallon, milligrams per liter (mg/l) or parts per million (ppm). One grain of hardness equals 17.1 mg/l or ppm of hardness.

The Environmental Protection Agency (EPA) establishes standards for drinking water which fall into two categories -- Primary Standards and Secondary Standards.

Primary Standards are based on health considerations and Secondary Standards are based on taste, odor, color, corrosivity, foaming, and staining properties of water. There is no Primary or Secondary standard for water hardness. Water hardness is classified by the U.S. Department of Interior and the Water Quality Association as follows:

Classification	mg/l or ppm	grains/gal
Soft	0 - 17.1	0 - 1
Slightly hard	17.1 - 60	1 - 3.5
Moderately hard	60 - 120	3.5 - 7.0
Hard	120 - 180	7.0 - 10.5
Very Hard	180 & over	10.5 & over

NOTE: Other organizations may use slightly different classifications.

Drops of Soap - A Hardness Test
Homemade Hardness Test - "Crude Test"

1. To 12 oz or 350 mls of water add dish detergent - one drop at a time. 2. Shake sample and look for suds. Count the number of drops. 3. When you see suds you are done.

Drops of Soap in 12 oz.	Hardness - mg CaCO3/L	Grains per Gallon	Classification
10	0 - 17.1	0 - 1	Soft
20	17.1 - 60	1 - 3.5	Slightly hard
30	60 - 120	3.5 - 7.0	Moderately hard
40	120 - 180	7.0 - 10.5	Hard
50	180 & over	10.5 & over	Very Hard

1. The phenolphthalein alkalinity, calculated as CaCO₃, should not be greater than:

15 ppm + (0.4