We thought we were done with math after high school was over and now it gets thrown at us all over again when trying to calculate our household needs.


When looking for a water softener the grain capacity and trying to understand what it means can be a little confusing, so we are about to break it down into small sections so that it can be understood better.

Water Softener Grain Capacity

The grain capacity for water softeners is how many grains the water softener can remove from hard water before it needs to regenerate. This means that the water softener may be able to pull the minerals out of hard water and make it soft, but it needs to drain them when it is full.

This is where a water softener calculator comes in handy. Here is a quick breakdown of how grain calculation works and an example.

There are 2 numbers you need to know the grain capacity needed: Gallons of water used every day and water hardness in grains per gallon.

To get gallons of water used each day and multiply it by the number of people in your household by the national average of water used daily per person by 70. (Ex: 4 people x 70 = 280 gallons used per day.)

The water hardness is the next part and only changes if you have iron present in your water. If so add 5 grains for every PPM of iron that is present in the water. So if you have 1 PPM of iron in your water but normally have 7 grains of hardness for your water, then you have 12 grains per gallon to account for.

Water Softener Sizing Chart

  Number of people in your house
Hardness in Grains Per Gallon1 to 2 people*3 to 4 people*5 to 6 people*7 to 8 people*
5-10 GPG32,000 Grain32,000 Grain32,000 Grain40,000 Grain
11-20 GPG32,000 Grain32,000 Grain40,000 Grain48,000 Grain
21-30 GPG32,000 Grain40,000 Grain64,000 Grain80,000 Grain
31-40 GPG40,000 Grain64,000 Grain64,000 Grain96,000 Grain
41-50 GPG64,000 Grain80,000 Grain96,000 Grain110,000 Grain
51-75 GPG64,000 Grain80,000 Grain96,000 Grain110,000 Grain
76-100 GPG80,000 Grain96,000 Grain96,000 Grain110,000 Grain
Choose the Proper Water Softener Based on the Hardness level And Number Of People In Your House.

An example from the grain capacity is this: As a family of 4 with hard water of 10 grains you will need to have a 24,000-grain capacity water softener because of needing 3000 grains of hardness to be removed every day for your families water use.

How Do I Know What Grain Water Softener to Use?

To know the correct water softener to use you will first need to figure out a couple of key pieces of information.

The first piece of information you will need to know is how hard of water you have in the city you live in. This can be done by getting a hardness test kit or by looking up your city and seeing the hardness of a city’s water supply, or the hardness of where you live, click here.

water hardness map
Water Hardness Map

The next step is to go to a water softener grain calculator like this one and fill the calculator in with your data and you will learn what size of water softener that you need.

Water Softener Grain Capacity FAQ

What Does 30,000 Grain Water Softener Mean?

30,000-grain water softener means that it is theoretically capable of removing that many grains of hardness before it needs to regenerate.

The hardness is the number of minerals that the water softener can take in before it needs to refresh and drain itself. The reality of a 30,000-grain water softener is that it was rated at that through controlled environments.

The real world is not a controlled environment so that 30,000-grain capacity is closer to around 27,500 grain capacity at max load.

At max load, this is not very efficient with how much salt is required to flush the water softener out. The most efficient range for a 30,000-grain water softener will be closer to somewhere in the capacity of 20,000 grains before needing a recharge.

Is A Bigger Water Softener Better?

A water softener that is bigger is not necessarily better. This is because you will still have one of the issues that an undersized water softener has inefficiency problems for salt consumption that can increase costs and increase trips to the store.

It can also end up causing resin bed issues due to being oversized, which is a different issue altogether. When a system does not get used often enough it can have resin bed damage and cause unnecessary maintenance costs.

The most efficient systems are ones that are built for the specific water needs of the customer. Not too small, not too big, but just right to where the water use keeps the system running smoothly without any hiccups.

Is It Bad to Oversize a Water Softener?

It can be a bad thing to oversize a water softener. This is due to the system not being used often enough. If a system is not used often enough the resin bed can be damaged, and if the resin bed gets damaged then the ability to produce soft water is hindered.

In the system being hindered then the oversized system can now become an undersized or ineffective system with the inability to capture the minerals from the hard water.

What is The Highest Grain Water Softener?

The highest grain water softener is going to be a 110,000-grain water softener. The ones that say they are higher than that do not soften water since they do not use salt.

By clicking here you are able to see what the current highest grain water softeners are. For the system to handle 110,000 grains before recharge it will be for a very high-water use household or building. This means that most will not need one that size or magnitude.

How Do I Know the Grains of Hardness in My Water?

The grains of hardness in your water can be figured out in two main ways. The first way is by looking up your city’s water treatment plant and figuring out what hardness of water your tap water is through their website. You can also use this map of the United States water hardness.

The second way is to go to your local home improvement store or order online a water hardness test kit to see what level of hardness the water is.

The way that the grains are known is by how many parts per million or grains per gallon of minerals are in the water. The minerals are what end up making the water considered hard.

Is 10 Grains Per Gallon Hard Water?

10 grains per gallon is going to be considered hard water. This is because there are 171 parts per million for minerals in the water when they are traveling through the pipes.

This can cause slight mineral deposit buildups with the water being this hard. It can also potentially cause dry skin but should not be that big of a health concern since that is on the lower end for city water hardness levels.

Final Thoughts

For the best experience with water softeners possible, you will want to get all the information needed to find the perfect water softener size.

If you end up trying to get an undersized or an oversized water softener, you are asking for trouble and frustration that you and your household do not deserve. It is better to take the extra time now and figure out the proper sized water softener. That way you hardly have to think of or worry about your water softener.


  1. https://qualitywatertreatment.com/pages/how-to-size-your-water-softener
  2. https://www.hydroflow-usa.com/water-hardness-map
  3. https://americanhomewater.com/how-to-size-a-water-softener-properly-foolproof-guidelines/

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