Home » Water Softening » Water Softener Guides » What Is Water Softener Grain (and How Much Do I Need)?

What Is Water Softener Grain (and How Much Do I Need)?

Scott Winfield
Written by Scott Winfield
Last Updated on

If you’ve done even a little bit of research on water softeners to get an idea of how to pick what you need, you’ve probably come across lots of talk about grain capacity. More often than not, the grain capacity numbers accompany the number of bathrooms the device can provide soft water for.

The fact that these numbers are associated together, plus the fact there’s the word “capacity” in the term, might lead you to believe that grain capacity has to do with how much water the unit can soften within a given period of time.

However, that isn’t exactly the case, as grain capacity is actually something that informs you of how much water hardness the unit can remove from the water in between its regeneration cycles (roughly 7 to 14 days, depending on the manufacturer).

There are two things to consider when figuring out what grain capacity you need: how hard your water supply is and how much water you really use within a day.

In this article, we’ll explain what water softener grain actually is, give you an idea about how much grain you need, and compare a system with a 48,000 capacity with a 64,000 one.

Water Softener Grain

Water Softener Grain
Water Softener Grain

As we said, water softener grain describes how much hardness a device can remove from water before it regenerates itself. For example, if a device boasts a 24,000-grain capacity, it means that it’s capable of removing 24,000 grains of water hardness between two regeneration cycles.

However, to get a real grasp of the term, we also need to know what water hardness means, how it’s measured, and how manufacturers test the grain capacity of their devices.

Water Hardness

Water hardness simply refers to how much calcium and magnesium ions are in the water. In the industry, it’s often measured in grains per gallon (gpg), but the United Nations Geological Survey (USGS) defines water hardness based on milligrams per liter:

  • 0 to 60 mg/L; soft water
  • 61 to 120 mg/L; moderately hard water
  • 121 to 180 mg/L; hard water
  • >180mg/L; very hard water

So, when it comes to water softening, it might be beneficial to translate these measurements:

  • One grain of calcium or magnesium equals 64.8mg of these minerals.
  • One gallon of water roughly equals 3.8 liters.

With that in mind, water hardness in grains per gallon is as follows:

  • 0 to 3.5 gpg; soft water
  • 3.5 to 7.0 gpg; moderately hard water
  • 7.0 to 10.5 gpg; hard water
  • >10.5 gpg; very hard water

Based on these measurements, how much water you use per day, and the regeneration period of your device, you can calculate how effective a water softener is.

Before deciding to purchase one, it’s important to check the grain capacity specification of the model you want while bearing in mind the hardness of your untreated water supply.

How Water Softener Manufacturers Test the Grain Capacity of Their Devices

The quality and quantity of the salt employed in the brine tank, the flow rate, temperature and pressure of the water itself, and the resin cleanness are all factors that determine the actual grain capacity of a water softener. However, that’s not how manufacturers test their devices, so the numbers they boast about might be a bit misleading.

Water softeners soften water through a technology known as ion exchange. In this process, the positively charged ions of minerals like calcium, magnesium, manganese, and iron are attracted to the negatively charged resin beads of the devices.

However, these resin beads can’t maintain their negatively charged status as they keep on trapping molecules. So, they need regeneration cycles to recharge and clear out the mineral residues that accumulate on them.

In traditional salt-based water softener systems, a brine solution prepared in the salt tanks of the devices is responsible for the regeneration process.

Water softener manufacturers often test their devices in carefully controlled laboratory conditions. They maximize the flow, pressure, and temperature of the water to get the best result while keeping the resin sanitated.

In other words, they create an unrealistic environment for their devices to perform optimally. So, when you see a device with 24,000 grain capacity, you should remember that, in practice, that may translate to a grain capacity of, say, around 20,000.

Most importantly, during testing procedures, manufacturers use the best water softener salt out there, and they use it in huge amounts to achieve the most efficient regeneration process possible for the resin. For instance, they regenerate resin that has 32,000 grain capacity with 18 pounds of salt, which is not sustainable in households simply because it’s going to cost too much in the long run.

On the other hand, most devices on the market work on 6 pounds of salt that can only regenerate the capacity of the softening resin up to 20,000. Yet, since the device is already programmed to 32,000 grain capacity, even when the resin consumes all that 20,000, it won’t fully regenerate. And the customer will probably have hard water for a couple of days until the device runs its pre-programmed regeneration.

Therefore, when in the market for a water softener, it’s important to consider this and lower the promoted grain capacity of a device by one-third. In other words, take it that the real grain capacity is closer to two-thirds of the marketed capacity. If the device says it has 32,000 grain capacity, it’s fair to assume that only 20k of it will be realized.

Luckily, though, the regeneration cycles of most devices on the market are re-programmable, and you can adjust them in accordance with your water-softening needs.

How Much Water Softener Grain Capacity Do I Need?

Water Softener Grain Capacity
Water Softener Grain Capacity

The grain capacity you need depends on the hardness of your water before it’s treated, how much water you need per day, and in what frequency the water-softening device will regenerate.

Of course, these three numbers vary from location to location and from household to household. What’s more, when it comes to water softener devices, we should also take into account the amount of iron in the water: 1 ppm of iron in water is considered to be equal to 5 gpg of water hardness.

So, if original water hardness results show, let’s say, 5gpg, you should add another 5 to it for every 1 ppm of iron found in your water. In the end, the grains you want to be removed from a gallon of water will be 10 (5 gpg + 5 for 1 ppm of iron).

According to the Environmental Protection Agency (EPA), an average US citizen uses 82 gallons of water per day. A family of four, then, consumes 328 gallons per day. When we multiply that number by the water hardness (10gpg as established in the preceding paragraph), an average family needs about 3,300 grains of water hardness to be removed per day.

Then comes the regeneration cycle. If a water softening device regenerates once every 7 days, then you’ll need to multiply the water hardness you need to be removed per day by 7, which in our example equals 23,100.

Bearing in mind the point we made in the previous section about how the manufacturers achieve their grain capacity numbers in lab conditions, you may want to also add 10k to 20k to that number. In our example, a device that has 32k to 44k grain capacity is the right choice for you.

In short, the equation you need to calculate your ideal water softener size is:

  • (Water hardness x Gallons of water you use per day at your household) x The number of days it takes for the softening device to regenerate

48,000 vs. 64,000 Water Softener Grain Capacity

Needless to say, a 48,000 water softener will remove less hardness from the water than a 64,000 one between regeneration cycles. That being said, which one you need depends on your water hardness and how many people live in your household.

Bearing in mind the calculations we made above, if you have extremely hard water that’s about 20gpg and have up to 4 people living in your house, a 48k softener might suffice. However, if you have at least 5 people in the house with extremely hard water, you might want to upgrade to a 64k water softener.

Water Softener Grain Capacity FAQs

What Do I Do When There’s Too Much Iron in the Water?

As we established above, 1 ppm of iron is equal to 5 grains of water hardness. However, moderately hard water with a high iron content might require more than a water softener.

More often than not, water softeners can handle only 2 to 5 ppm of iron in water. If the iron levels in your water supply are higher than 5 ppm, you should complement your softening system with an iron filter.

Can a Water Softener Have too Much Grain Capacity for a Household?

No, a water softener with too much grain capacity will function just as efficiently, if not more, than a water softener with a lower grain capacity. However, grain capacity isn’t the only criterion that you need to consider while sizing up a water softener.

The flow rate and water pressure of a device are also important. More often than not, the higher the grain capacity of a device, the faster its flow rate and water pressure.

If the flow rate at your household is too slow for the device, then it’ll be less efficient. Water softeners need a certain flow rate that’ll be specified in the instruction manual to function and regenerate properly. A slower flow rate than the device requires means that it won’t regenerate sufficiently, and it’ll probably stop doing its job after a while.

Also, an oversized water softener will simply be more expensive than a suitably-sized one.

What Can Go Wrong If I Already Installed an Undersized Water Softener?

A lot of things. First of all, a device with an inadequate grain capacity won’t soften enough water for your household needs, so you won’t reap the benefits of a properly sized water softener.

Additionally, it will regenerate too frequently, and therefore, it’ll consume too much salt, which will be quite costly in the long run. And, too much regeneration will reduce the device’s lifespan, so you’ll need to replace it sooner rather than later.


The grain capacity of a water softener simply indicates how much water hardness the device will remove between two regeneration cycles. The original water hardness of your water supply and how many gallons of water you and your family members use per day are the two main factors that determine how much grain capacity you need from a softening device.

In addition to those, you should also remember that the numbers the manufacturers use to promote their devices can be misleading. They test their devices in optimized laboratory conditions that are difficult to meet in real-life American households.

So, even if you carefully calculate what size water softener you need, it’s best to add a couple of thousand to that number. That way, you’ll be purchasing a more efficient device.

However, it’s recommended that you don’t get a needlessly oversized device as it might falter when the flow rate and water pressure at your house can’t meet its needs. Once you’re certain about the water softener size you need, you can head to our guide on the best water softener systems on the market to pick one accordingly.

Sign Up for Weekly Water Quality News & Advice

Join our 1 Million+ strong water defense community and get updated on the latest product news & gear reviews.

We HATE spam. Your e-mail will never sold or shared!

Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
Leave a Reply