Levels of hardness have been established.

What does GPG or grains per gallon mean?
Parts per million or grains per gallon are both used to describe the dissolved hardness minerals contained in a water. One part per million (PPM) is one unit of a substance out of one million units of water. Grains, or grains per gallon (GPG), is a unit of weight. It is 1/7000 of a pound. One GPG, (1gpg) is equal to 17.1 PPM.

What problems does Hard Water cause?
Hard water is fine for many uses around a home. To water a garden, wash down a driveway and general outdoor lawn care, most water, as it comes from a well or from a municipal treatment plant, works fine. But for indoor use such as bathing, showers, doing dishes and washing clothes, shaving, washing china and flatware, and dozens of other uses, hard water is not as efficient or convenient as "soft water."

Efficiency Advantages of Using Soft Water:
• You will use less soap and other cleaning products.
• Reduce the difficult to clean "soap scum" and 'bathtub ring'
• Soap Scum stays on surfaces leaving unsightly spots on dishes, glass ware and flat ware.
• Heating hard water in the water heater, forms hardness scale. This scale plugs plumbing and builds up on the inside of water heaters, It can cause increased electric or gas bills, and may lead to early failure of the appliance with costly replacement necessary.
• Soap scum is difficultto remove and stays on your skin after bathing or showering. It clogs skin pores and coats hair. This residue may be a breeding ground for bacteria, and could cause diaper rash, rough, red hands, skin irritation and skin discomfort.
• Hardness minerals may cause unwanted taste in cooked foods such as vegetables and cause cloudy ice cubes.

Where Can Water Hardness Information Be Obtained?
For municipal water supplies, call the water department or the local City government, they will provide the answer. To obtain additional information about a water supply, THE WATER DOCTORS can have your water tested through a laboratory analysis. 
Such an analysis may be either bacterial, micro biological, or chemical, depending on the purpose. Chemical analyses made our labs show iron in milligrams per liter and hardness minerals in grains per gallon or milligrams per liter.

Use of both grains per gallon and milligrams per liter is a practice followed primarily for convenience in reporting concentrations of minerals, some of which are abundant in water and some of which are found only in trace quantities.

Actually there are four units of measure commonly used in water analysis work: milligrams per liter (mg/l) or parts per million (ppm); grains per U.S. gallon (gpg); equivalents per million (epm); and grains per imperial gallon (gpg imp). To convert from milligrams per liter or parts per million to grains per gallon, divide the former by 17.1. Similarly, multiply grains per gallon by 17.1 to arrive at milligrams per liter or parts per million.

Remember: that 17.1 PPM (parts per million), equals 1 GPG. Look at the following example of how to determine water hardness.

If the water department says the water supply has 350 PPM of calcium.

Hard Water. What Can Be Done?
If water tests over 1 GPG hard, consider softening it with a water conditioner.

There are only two practical ways to treat hard water: 

The process consists of flowing the hard water over a bed of plastic Resin beads. On each bead, slight electric charges hold sodium ions on the surface of the bead. However, these beads also have the ability to attract and hold hardness minerals. As hard water flows through the water softener, it passes around the plastic beads. The hardness minerals (ions) in the water have a greater attraction to the bead than the sodium on the bead. Therefore, they attach themselves to the bead, and in the process they displace the sodium ions. Thus the name ion exchange. Hardness ions are exchanged for sodium ions.
 

Eventually, the plastic resin bead will be covered with hardness ions. When this occurs, the removal of hardness will come to a stop. The water softener in this condition is known as being exhausted. In order to remove additional hardness from the water, a means must be found to clean the resin beads of accumulated hardness ions. This is accomplished by a process called regeneration. A brine solution is introduced into the resin tank. The extreme concentration of sodium ions in the brine solution scrub the hardness ions from the resin beads. The resin material is then flushed with clean water and the excess brine and accumulated hardness is flushed away, leaving the beads ready to remove additional hardness.