You can measure water hardness with simple soap tests, commercial test kits or expensive electronic testing machines. Some hardware stores and online retailers, such as Amazon.com, sell test kits. Water may also be acidic or corrosive, which is tested for using different methods.
To measure water hardness using the soap method, fill a glass bottle that can be sealed with 12 ounces of test water. Add drops of dish soap one at a time, sealing the bottle and shaking it after each drop. Keep adding more soap drops until soap suds form when shaking. The more soap it takes to form suds, the harder the water must be. Under 20 drops of soap means the water is soft or slightly hard. Water is medium-hard at 20 to 40 drops of soap, and very hard above 40.
Commercial hard-water test kits vary greatly in design. One common test-kit type comes with test strips that are dipped in the water and change color depending on the hardness of the water. Another test-kit type is merely a packaged soap test.
Hard water causes calcium and magnesium buildup on plumbing fixtures and makes washing more difficult. Fix hard-water problems permanently by installing a water softener. Stores sell many types of water softeners, including the common two-tank system.