NOTE: As an Amazon Associate, I earn from qualifying purchases.  Learn More.

water softener grain capacity

Grain Capacity-Understanding True Water Softener Capacity

On the internet, in each big box store, and local water softener shops you will find water softeners rated by their “grain capacity.”

This rating is unfamiliar to people who are new to the science of water softening, and salespeople often gloss over it likely because they do not understand its implications in selecting a water softener.

So let us define the term.

Grain capacity is the amount of hardness which can be removed by a water softener before it has to regenerate.

Water softeners use a form of ion exchange to remove hardness from water. 

A water softener catches ions of magnesium and calcium and replaced by ions of sodium.

The grain capacity of a softener is a measure of the amount of magnesium and calcium compounds that can be removed from the water, before the softener is saturated, and should be regenerated.

Note: A single grain is approximately 65 mg - about the weight of a cereal grain like wheat or rye.

What is so complicated about grain capacity - and we agree it is not a good way to discuss water softener capability - is that the grain capacity of any water softener is changeable.

That is right - a water softener rated as a 32,000-grain softener might also be known as a 20,000 grain or 25,000-grain softener. 

But how can this be?

Why Grain Capacity Isn’t Fixed

First, you have to keep in mind is that your softener will remove hard water by using about one cubic foot of resin, and the adhesive has to be restored from time to time.

Read the following very carefully - it is not the most natural thing in the world to explain:

So, a 32,000-grain capacity water softener should have the ability to eliminate 32,000 grains of “hardness" until you want to regenerate it, right?

Nope, this is not right.

If tested under laboratory conditions, the softener will eliminate this amount, and that is because things such as water pressure, temperature, and flow are monitored closely.

These so-called perfect conditions rarely occur anywhere but in a lab, and this is where the drift incapacity begins.

Every home is different, and if you use a water softener when you are on a trip, the water requirements are much more precarious.

So a 32,000-grain capacity water softener will likely only cope with about 28,000 -- 30,000 grains before regen is needed.

Talking about regeneration, when you have to perform an improvement on a water softener of this size, you’ll need a minimum 30-36 lbs of salt per cubic foot of resin!

Shocking? Many manufacturers neglect to mention this little statistic.

It's possible to regenerate a water purifier using just 5-7 lbs of salt. But when this is done, it is only going to yield a 20,000-grain capacity.

In short, 1/3 salt produces 2/3 more capacity.

Cutting the amount of salt is very common in homes, because it is more affordable, helps the environment and creates less strain on your arms.

How Water Softener Capacity Needs to Be Explained

In some states throughout the USA and Canada, it is a legal requirement to mention the capacity of a water softener by using the amount of salt it will require per regeneration and the cubic feet of resin.  It is indicated regarding the grains used per pound of salt.

This is a much better and much more accurate method of telling customers what they could expect from their water softener concerning efficiency.

How Many “Grains of Water Softener” Do You Really Need?

Know Your Water Hardness

 Water Softener Grain Capacity

You already know that minerals are measured in "grains." And water is measured in gallons.  

So, water hardness is measured in terms of grains per gallon, or GPG for short.

Water hardness ranges from 0-1.0 GPG, and the hardest can be everywhere above 10.5 GPG.

Note: A "grain" is equal to 1/7000th of a pound.

You can measure water hardness using a testing kit or, if you are on government supply, the hardness level can be found on the internet in your regional water utility's annual reports.

How Much Water Do You Consume?

Next, consider how much water is used in your household.

The average person uses about 75 gallons daily, so multiply 75 from the number of people in your home.

That may seem too much - but think about every shower, a load of laundry and bathroom flush - it adds up!

Grain Capacity

When you’ve figured out your daily water consumption in gallons, the final step is to multiply that amount times the GPG hardness of your water.

The final total will be the "grain capacity," that is the number of grains which will require to be removed daily to maintain your water soft.

A higher grain capacity means you need a bigger water softener.

Example: Four people in the home X 75 gallons X 150 GPG water harness = 45,000 grains that will need to be eliminated daily, or "GPD."


Most water softeners must restore, or clean, their resin bed about once a week.

The resin bed within the system gets coated with hard water particles, so it must recycle the water used so it can continue to produce pure water.

It's important you buy an appropriately-sized water softener to prevent regenerating too often and squandering money, or not restoring enough and the machine wears down too quickly.

Keeping your water clean is essential to maintaining your household safety.

When you have questions regarding softeners or water hardness, contact an expert to match you with the best-sized water softener you need for your home.

Final Thoughts

Water Softener Grain Capacity

The concept of “grains” has been around for a long time, but there are many salespeople - both online and in-store - that do not know this term or neglect to accept its validity.

However, rest assured that the salt use data provided by resin suppliers don't lie.

When you are choosing where to buy your softener, make sure you find a dealer that understands this page and can help you pick a water purifier which will reduce salt utilization and maximize your satisfaction - without wasting money on energy or premature replacement of a worn-out system.

Additional References:

Ed Carmichael

About the Author Ed Carmichael

Ed is a water specialist in Tampa, FL. He built to help his friends and family learn about DIY solutions to common water quality issues in the home.

follow me on:

Leave a Comment: