Buying Guide

Types of Water Softeners

What is Water Hardness
Rust forms at the edges of a sink drain.
  • While rainwater is “soft” when it falls from the sky, as it flows into aquifers it can absorb minerals such as calcium, magnesium and trace metals. While safe to drink, hard water can inhibit the effectiveness of soaps and detergents, which can result in bathtub rings, spots on glasses and dishes, less effective clothes washing and less effective rinsing of soaps and shampoos. 
  • In addition, deposits from hard water can leave scale deposits and mineral build-up in coffee makers, water supply pipes, ceramic tile and water heaters. This can reduce the water flow, shorten the lifespan of a water heater and cause long-term damage to plumbing and fixtures. 
  • You can use a water testing kit to determine your water’s hardness level. A level of 1 grain per gallon (gpg) or higher technically indicates some water hardness, but 7 gpg often indicates that a water softener may be needed at your home. 
What Size Water Softener Do I Need
A faucet fills a glass with water.
  • A quick way to determine the best size water softener for your house is to calculate the average number of gallons your household uses in a day. You can determine this number by multiplying the number of people in your household by the average number of gallons used per day (usually around 75.) Then multiply that number by the hardness level in gpg you found when you tested your water. 
  • For example, if you have four people in your household using an average of 75 gallons a day, and your water test shows that your water hardness level is 7 gpg, your math would look like this: 4 x 75 x 7 = 2,100. Look for water softeners that can process at least 2,100 gpg daily. 
How Do Water Softeners Work
A person adds salt pellets to a water softener.
  • Water softeners work by filtering hard water through a mineral tank. The tank contains a bed of plastic beads or resin beads that have negative electrical charge. The negative charge of the water softener resin attracts the positive charge of such “hard” particles as calcium and magnesium, leaving them on the beads and removing them from the water. 
  • Over time, the water softener runs a regeneration cycle to clear the hardness particles from the beads. The unit’s control valve sends a mixture of salt and water from the brine tank into the resin bed. The salt attracts the minerals from the beads, and the excess debris is flushed from the system and down the drain. 
  • Regeneration cycles occur at least once a week, but often more. The frequency of regeneration cycles depends on numerous factors, including how hard your water is and how much water you use. The harder the water and the more water used, the more frequent regeneration cycles will need to be. Regeneration cycles use about 50 gallons of water on average, but this will depend on the water softener system. Unless you have a dual-tank water softener, the equipment cannot be used during the regeneration cycle. 
  • Resin beads do not need to be replaced. However, to maintain your water softening effectiveness, periodically refill the brine tank with water softener salt. The frequency with which you will need to replace the salt depends on your water softener system’s salt tank size and how often regeneration cycles occur. 
Ion Exchange Water Softeners
An ion exchange water softener.

Of the various types of water softener systems, the most common are ion exchange water softeners, dual-tank water softeners and salt-free water softeners. 

  • Ion exchange water softeners use the method described above to exchange ions, or electrically charged particles, in a water supply. They usually substitute sodium ions for the ions of magnesium, calcium, iron and other hard minerals. 
  • Ion exchange water softeners require periodic refills of water softener salt. While these kinds of water softeners add minute amounts of sodium to drinking water, they may not be ideal for people trying to reduce the sodium in their diet. 
Dual-Tank Water Softeners
A dual-tank salt-free water softener.
  • Dual-tank water softeners are ion exchange models that contain two resin tanks so that one tank is always available for use while the other is in the regeneration cycle, ensuring that a household can access soft water any time of day or night. 
  • This option tends to be more expensive, but may appeal to large households, homes with high water usage or ones with irregular schedules that would be inconvenienced by a night-time regeneration cycle. They tend to take up more space than single-tank water softeners. 
  • Salt-free water softeners also have dual-tank models.
Salt-Free Water Softeners
A salt-free water softener.
  • Salt-free water softeners use a potassium-chloride salt substitute instead of sodium. Water conditioners don’t reduce the hard minerals in your water, but instead prevent them from building up in pipes and appliances. Potassium is considered more environmentally friendly but is also more expensive than sodium. People concerned about their sodium intake may prefer these types of softeners. 
  • In addition, water conditioners, reverse osmosis systems and magnetic water softeners are often grouped with these systems, but use different filtration methods and are not considered true water softeners, although none of them use salt.
Water Softener Features and Installation
The control panel of a water softener operating in a basement.

In addition to the dual tank designs, water softeners can include special features. 

  • Timer controls can recharge the machine at a set time of day, but tend to be most effective if you consistently use the same amount of water every day. 
  • Demand-initiated regeneration (DIR) controls detect when the resin needs recharging, which can use salt and regeneration water more efficiently and reduce waste. 
  • Homeowners can install a water softener by following instructions in the owner’s manual, but may find it easier to consult a professional when installing a whole-home system. 
  • The Home Depot’s whole-house water softener installation service professionals are local, licensed, insured, and have undergone a thorough background-screening process. Learn more about The Home Depot’s water treatment system installation services, which include free in-home consultation.


Tip: Salt-based water softeners are restricted in some communities, so check the codes in your area before installing one. 

Through the removal or hard water minerals, softened water generally goes easier on your plumbing and makes detergents and other soaps more effective. The right type of water softener installation can make a difference in how smoothly things flow around the house.