Water softeners are sold in several sizes, each rated by the number of grains of hardness they can remove from water between regenerations. Softener units rated from 12,000 to 16,000 grains are considered small, medium-size units can handle 20,000 to 40,000 grains, and large-capacity models upwards of 40,000 grains.

You can calculate the size of water softener your family needs by multiplying the number of people in your household by 75—the average number of gallons used per person per day—to figure out the total amount of water your household uses daily. Then multiply this number by the number of grains per gallon (GPG) of hardness minerals in your water to figure out the capacity of whole-house water softener you need.

Why we like it: • Does not require salt or periodic backwashing • Treats water for the entire house • Relatively easy to install

So, for example, if you have a family of five, figure 375 gallons of water are used per day (5 X 75). If your water has 10 GPG, multiply 375 by 10 and you have 3,750 GPG requiring removal each day.

Compare this to the recharge cycle of the unit you’re considering to see how frequently regeneration must occur. The idea is to get a unit that will go at least three days between recharges. Ideally, the water softener can also handle periods of larger-than-normal water usage.