- Take into consideration the number of people in your household. The size of your household, and therefore the number of gallons of water being used every day, will determine the size of the water softener you need.
- Look for a softener that will work for your level of water hardness. If you don't know your water hardness level then have it tested at a lab.
- Determine your household's minimum softener capacity needs. This is the daily hardness to be removed (see the Tips section for calculating this number) multiplied by the number of days you want to go without the softener regenerating (usually 2 or 3).
- Decide whether you need your water softener to remove iron, since not all softeners will remove every kind of iron. Again, if this is something you're unsure of, have your water tested by a local laboratory.
- Check the size of your water supply line prior to buying a new water softener, especially if your home is relatively new. If your main water supply line is one inch or larger then you will need a higher flow valve on your water softener.
- Choose a softener based on what controls the regeneration. Some units are controlled by a timer but don't account for unusually high usage rates and regenerate whether doing so is necessary or not. Demand-initiated regeneration units compensate for these problems and regenerate only when necessary.
- Calculate your total daily water need by multiplying the number of people in your house by the average number of gallons used per person daily, which is around 80. Then multiply that number by the grains per gallon of hardness in your water to get an idea of how much hardness your softener will need to remove on a daily basis.