Water Hardness Test Procedures

Water hardness is not a health hazard--the EPA considers it an objectionable.

There are many ways to test the hardness of your water. For years the "soap test" was used, but professionals prefer to use the titration method for a more accurate reading. Water professionals measure water hardness using complicated formulas and laboratory equipment. Calcium and magnesium are two of the most common minerals that are responsible for causing water hardness. The Environmental Protection Agency (EPA) considers water hardness to be an "objectionable," meaning that it sometimes causes objectionable tastes in water, but it is not currently considered a health hazard. There have been no standards set for human consumption of hard water.

The Try-at-Home Soap Method

While not scientifically accurate and considered a qualitative test and not a quantitative one, the soap method will allow you to determine if you have hard or soft water in your home. Fill two glasses halfway, one with water from the tap and the other with distilled water. Place 10 drops of dishwashing soap into each glass. Individually, cover each glass with your hand and shake it up until the soap foams. The distilled water will be foamy and have lots of suds---this is the measure of soft water. If the glass of tap water has little to no suds, then you may assume you have hard water.

The Titration Method

At any public water treatment plant you will find a lab that has a sink with constantly running water. This ensures that the water being tested is actually the water that is being stored in the system, i.e., the basin or clear well, rather than the water that just sits in the pipes. Water is titrated with a sodium ethylene, diamine tetra-acetate (EDTA) solution to obtain a reaction from any calcium and magnesium in the water. The standard EDTA solution will show red in the presence of calcium and magnesium ions and blue when they are not present. Reagents used with this solution include the hardness indicator powder and the hardness buffer.

To test the hardness of water, place a 50 ml sample of water in a 250 ml glass flask. Add 1 dipper of the hardness indicator powder, then add .50 ml of the hardness buffer to ensure the pH stays around 10. The mixture will turn red if hardness is present.

Total Water Hardness Test Kits

While not quantitatively accurate, this method is easy to obtain and use to determine water hardness in your tap water. Purchase a water hardness test kit online or from a store that specializes in swimming pool equipment and supplies. Each bottle will contain several test strips and will cost between $8 and $14. Turn on your water faucet and let it run to ensure you are obtaining water from your supply, rather than what is in the pipes. After the water has run for a few minutes, take a test strip out of the bottle and hold it under the flowing tap water for 2 seconds (this may vary depending upon the manufacturer). Shake the strip to remove excess water. Compare the color of the strip to the color chart on the side of the bottle or on the paper that may have come with the kit to determine the level of water hardness.

References

• Environmental Protection Agency: Drinking Water Glossary
• Gannon University: Determination of Water Hardness by EDTA Titration