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What Size Water Softener Do I Need?

Hard water can definitely be hard on your household. From discolored spots on your favorite china to tap water that tastes less-than-refreshing, hard water can impact so many aspects of your day-to-day life. If you’ve pondered the thought, “do I need a water softener” and decided to invest in one to remedy hard water’s effects on your home, you may already be dreaming of spotless plates and delicious glasses of water right from the tap. 

But before you can start reaping the many benefits of a water softener, you may be wondering, “What size water softener do I need?” 

The answer depends on the hardness of your water, the size of your house, and how much water you use . In this guide, we’ll discuss water hardness, how it impacts water softener sizing and the type of water softener you’ll need, and the equation you can rely on to calculate your ideal water softener. 

What You Need to Know to Determine Your Water Softener Size

Thankfully, you don’t need a degree in water science or advanced mathematics to calculate the perfect size water softener for your household. You just need to know two things: 

#1 Your home’s water hardness levels – A water’s hardness level is determined by how many grains of dissolved minerals (specifically calcium and magnesium) are in your area’s water source. The more mineral grains in your water, the harder the water will be and vice versa for soft water. The harder the water, the more work your water softener will have to do to remove those minerals for optimal results. This is why water softeners are sized by grains rather than household. 

Water hardness will vary based on your location, as different regions will have different factors impacting the water (factors include climate, geological make-up of water source, and even the age of your area’s public water filtration systems). Check out your zip code’s drinking water quality report (available online) to learn more about water hardness levels in your city water.

You can also purchase a water hardness test kit online or at your local home improvement store if your local water department cannot provide hard water mineral levels. You can also take water samples and send them to one of the testing labs listed on the United States Environmental Protection Agency (EPA) website as an alternative.1

#2 About how many gallons you use every day – For an accurate estimate, take a look at your water bill and divide the gallons used by the number of people in your home. Or, you can simplify this step by using the national average daily water use. According to the U.S. Geological survey, Americans use between 80-100 gallons of water a day.2 Multiply this number by the number of individuals in your household and you’ll have a rough estimate.

Why is this number important for your calculations? The more water used, the more grains will need to be removed. 

Water Softener Systems starting at only $35/mo. Try before you buy!

The Water Softener Size Equation (Simplified)

Ready for a little water softening math?

Multiply the daily amount of water used by your household (in gallons) by your home’s water hardness (in grains per gallon). Then, multiply that number by seven since a water softener will   ideally regenerate every seven days. 

The final result is the number of grains your water softener will need to remove every week. 

Let’s work with an example to help see this equation in action. Meet the Armans—the Armans are a family of four and are excited to find a water filtration system for their home in Escondido, California. The Armans took a look at their water bill and discovered their water consumption was up to  360 gallons per day on average. Their neighborhood has a water hardness level of 12 grains per gallon. 

Let’s plug that into our equation: 

  • 360 gallons X 12 grains = 4,320 total grains every day
  • 4,320 X 7 days between softener regenerations = 30,240 grains to be removed every week.

Now that you know how many grains your water softener will need to remove, you can start shopping for the accurate size.

A Quick Guide to Water Softener Sizes

Water softener capacity is a bit more specific than “Small,” “Medium,” or “Large” which is why choosing the right size water softener takes some background knowledge. Water softeners are categorized by grain capacities. The following are the most standard sizes: 

  • 24,000
  • 30,000
  • 32,000
  • 48,000
  • 56,000
  • 64,000

Most families of four that have water with a hardness scale of five or ten grains per gallon (GPGs) would need a 30,000-grain capacity water softener. 

However, any four-person household with a 15 or 20 GPG water hardness score would typically need to use a water softener system with a 40,000 grain softening capacity

With that in mind, it’s important to choose the right water softener. Let’s revisit the Armans and their 30,240 grains of minerals. They would probably choose the 32,000 size. 

Can You Get Too Big of a Water Softener?

When in doubt, size up. Why? Because a system that is one step up in size may process grains more efficiently, making it more ideal for your family.

However, it is possible to purchase a water softener that can process more water and grains per gallon than you need. This increased processing may not only waste water but also over-soften your water. There are several side effects associated with this, including:3

  • The introduction of excess sodium into your water
  • Increased sodium in the plumbing lines leading to pipe corrosion 
  • The emergence of regeneration issues, increasing the potential for in-tank bacterial growth

Can You Choose a Water Softener That’s Too Small?

Absolutely. It’s not ideal if you purchase a water softener that’s too small either. It may overperform, causing its motor to go out sooner than it otherwise would have. The water softener system may also experience flow rate issues, meaning it doesn’t treat water as efficiently as it once did. 

Keep In Mind What You’re Using Your Water For

The amount of water usage you and your family use and what you’re using it for can significantly impact your water softener needs.4 You may, for example, have a higher demand to remove minerals in your water supply if you’ve developed a rash or are washing a baby’s clothes than if you’re planning to water your family’s lawn. That is also why it is important to know how to add salt to your water softener to reduce the amount of irritation on your skin. 

Bottom line? If you have a pressing need for soft water, go bigger. 

Find the Perfect Fit with Rayne Water

If you have hard water and want to soften your water to soothe dry skin or to help protect your home’s plumbing, finding the right water softening system is a bit like living your own version of Goldilocks and the Three Little Bears. To find your “just right,” you’ll need a little know-how and of course, the support of a trusted professional. 

Our water conditioning experts here at Rayne Water are eager to learn more about your water softening needs and recommend the right product to improve the quality and taste of your water. Find your happily ever after (and your softest water yet) with Rayne Water. 


  1. United States Environmental Protection Agency. Contact Information for Certification Programs and Certified Laboratories for Drinking water.
  2. United States Geological Survey. Water Q&A:
  3. Minnesota Department of Health. Home Water Softening.
  4. Family Handyman. How to Choose the Right Water Softener.
  5. Urdesign. What Size of Water Softener is Best for Your House?