Father's Day Sale: Get 50% Off Plus Free Shipping

How to Size a Water Softener Quickly and Easily

How do you know what water softener size to buy? How big of a water softener do I need? What’s the difference between a 30k grain capacity and a 50k grain capacity?

In this article, we’ll help you figure out how big a water softener you need to buy.

Water Softener Capacity

Why are some of the same models of water softeners labeled with different “capacity” limits?

In an ion exchange water softener (i.e. a lot of water softeners available on the market), the capacity limit refers to how much hardness the system can remove before it needs to regenerate. Regeneration is when the salt is run through the resin so that it’s refreshed, active, and ready to remove more hardness ions.

So, you might be thinking,that’s great and all, but what’s it have to do with me?

Why does the capacity affect the type of water softener you need? The answer is really simple: You need a bigger water softener if you have a bigger water demand, so to speak, than others. For example, if you have a large family, you might need to run the dishwasher, laundry, a couple showerheads, and the kitchen sink all at once.

Water Softener Size - 5 Factors You Need to Know

If you try to run water during the regeneration process, there will be a handful of possible outcomes depending on the quality of your water softener. In the best case scenario, the water will flow just fine, but the water softener won’t be working. You’ll be getting hard water. On the other hand, it’s likely you’ll experience some flow restriction (low water pressure) on top of hard water. If you’re unlucky, you might not be getting any water at all during regeneration.

In short, you want your water softener to regenerate at night. If you buy the wrong size, it’s going to regenerate at some point during the day.

What Size Water Softener Do I Need? 

So, now you might be thinking, why don’t I just buy the biggest water softener available, then?

And there’s another simple answer: because you’ll spend much more than you need to. 

Here’s an additional issue: there’s a possibility that, even if you live in a household with a larger water demand, you can get away with a “smaller,” lower-grain-capacity water softener because your hard water problem isn’t that great.

Luckily, here’s a simple way of figuring out the grain count that you’ll need:

  1. How many people do you have in your home?

  2. Multiply that number by 100 (the higher end of average water use per day for most people, according to theUSGS).

  3. Multiply that number by the grains per gallon of hard water that you have (which you can find by buying a testing strip online). The average grains per gallon in the US is hard to determine. It’s likely anywhere from 6-10 grains per gallon, if you’re running into serious hard water issues.


Where does that leave us? Well, if you’re looking at higher-end figures and just trying to get a guesstimate of your water softener size, we can make a general estimate. Start with a 30k grain capacity (because you’re probably not going to find a water softener with a lower capacity than that), and add an additional 10k of capacity for every person in your household above 3 (a 3-count, not three years old). For example:

  1. For 1-2 people, look into buying a water softener that’s at least 30k grain.

  2. For 3-4 people, 30k-40k grain capacity water softeners should work.

  3. For 4-6 people, go for 40-60k.


How Many Grain Water Softener Do I Need?

Fleck 9100SXT Water Softener | Dual Fleck Water Softener

However, this is just a ballpark figure. It massively depends on the hardness of your water and how much water you use. If you want a more accurate figure, you’re going to need more accurate variables.

What are the Different Sizes for the Different Types of Water Softeners? (Ion Exchange and TAC)?

The above guide deals with how to size a water softener for ion exchange, salt-based water softeners. What about template assisted crystallization water softeners like those we offer here at FilterSmart?

If there’s no need for regeneration, since there’s no salt, how do you know what size to buy?

Well, since there isn’t a grain capacity for template assisted crystallization (as it applies to hardness, not the filter), all you need to know is how many gallons per minute of water you need, and that’s largely based on the number of bathrooms in your home. 

For example, if you want to buy the FS1000, you’ll see a dropdown menu asking you how many bathrooms are in your home (or, alternatively, how many grains per minute you desire). Generally, our smaller whole house systems can handle 12 gallons of water per minute just fine, and the bigger systems handle 15 gallons.

There’s no need to calculate the exact grains per gallon of hardness or your exact water use per day. You’re not going to run into the same issues with our systems.

If you live in a smaller home with 1-3 bathrooms, go with the smaller 12 gallon per minute system.

If you live in a bigger home with 4-6 bathrooms, go with the larger 15 gallon per minute system.

It’s that easy.

Conclusion: How to Size a Water Softener

What is grain capacity? How can you quickly find out what size of water softener you need? And why is it so complicated?

In this article, we gave you a quick and easy way to find out the water softener size for you: start with a 30k grain capacity. Very few water softening systems are going to be lower than that. Then, for every person in your household above a three-count, add another 10k of capacity. So, if there are four people living with you, that means you’ll probably need a 40k capacity water softener. 6? 60k. So on and so forth.

Keep in mind that this is a general guesstimate, at best. If you want to know the exact size, you need to figure out the exact hardness of your water and the exact water demands of your household.

On the other hand, if you want to buy a FilterSmart salt free  system, it’s much easier.

1-3 bathrooms? 12 gallon per minute system. 4-6 bathrooms? 15 gallon per minute.

Questions? Concerns? Feel free to get in touch:

Call us: 866.455.9989

Email us: sales@filtersmart.com 

As seen on: