Metropolitan Government of Nashville and Davidson County prepared this information.  It also is available on their website at

Soft water is neither healthy nor desirable for drinking! If you were a steam iron or a washing machine it would be great, but we are neither! There are good reasons you should not be drinking soft water!

Water is a universal solvent. Most materials, especially metals, are partially soluble in water. If that water is heated or softened it becomes much more aggressive at leaching metals from water lines. Lead in soldered joints and copper in pipe are particularly vulnerable and these are two of the heavy metals which shouldn't be present in significant amounts in your drinking water.

Calcium and magnesium are two minerals which make water "hard." Both of these minerals are classed as "contaminants," but that's a poor choice in terminology, for calcium is essential in our diet! A softener merely exchanges one group of non-toxic elements for another group of non-toxic elements. Water hardness is measured either in grains per gallon (GPG) or as calcium hardness in milligrams per liter (mg/l) or parts per million (ppm). GPG is based on calcium hardness. To convert from calcium hardness ppm, just divide by a factor of 17.2 and this gives you hardness in GPG. A soft or slightly hard water has up to 3.5 GPG; moderately hard water runs from 3.5 to 10.5 GPG; and very hard water is greater than 10.5 GPG. If your water is over 7 GPG, you might want to consider a softener just for the laundry.

Metro water is on the low side of moderately hard at 4.1 GPG (that is 70 mg/l of calcium hardness. This is an excellent value and highly desirable! Cities which have soft water are having difficulty meeting the new lead standards in tap water. Metro has had none of these difficulties in meeting the new standards!

A soft water is aggressive at leaching metals (like lead) from your lines and faucets. Most faucets are solid brass (with a relatively high lead content) and are chrome plated. This means that if you have soft water, there is a great chance that your initial drawing of cold water will have a higher lead content than normal. Hot or warm water from the tap should never be used for cooking, shortcuts, drinking water, beverages, or infant formula as it could be higher in heavy metals like lead!

Besides making the water more corrosive and aggressive at leaching metals from your lines and fixtures, the zeolite beads from water softening systems may back-siphon into your toilet tanks, and the soft water may attack vital plumbing parts. While supposedly solving one set of problems, the softener could possibly introduce other problems which you may or may not be aware of! A water softener, besides leaching lead and other metals from your plumbing, can increase your sodium intake. In a water softening device hard water flows through synthetic resin beads. Sodium ions (salt) are loosely attached to each bead and the water exchanges hardness ions (calcium and magnesium) for the soft sodium ions. These devices can also be costly to run since they can waste up to 120 gallons for every 1,000 delivered.

A water softener is not designed (nor is it effective) to remove lead and other metals, chlorine, taste/odor compounds, nor chlorine by-products. Its purpose is only to make a hard water soft. Water treated to remove chlorine may encourage the formation of black rings in toilet bowls!

Soft water is great for laundry, bathing, steam irons, and auto batteries, but definitely not for anything else. If you are contemplating installing a softener, there are serious questions you should ask: who will test the effectiveness of the softener, how often will these tests be run, and how will my drinking water quality be affected?

Metro Water Services does not test any home water treatment device, including softeners, and does not recommend the use of particular devices!