How To Know What Water Softener Size You Need

Last Updated on December 12, 2022 by Mattias

Choosing the correct size for a water softener is essential, not only to make it fit. But to also get the most out of it.

This article will answer the question, “What size water softener do I need.”

We will go through what you must know before buying a water softener and why you need to know it.

Consider this the ultimate guide for water softener sizing.

How To Size a Water Softener

To calculate the water softener size, you must know a few things first. Because if you figure out the correct size water softener, you may need less salt and maximize your water softener capacity.

The first step is to calculate your daily softening requirement. By calculating how much your water softener needs to remove daily, you can find the right size water softener just for you.

First, you must know your water’s hardness level and daily water use.

Read also: 12 Best Kitchen Faucets For Hard Water + Buyers Guide

The Hardness Of Your Water

Knowing your water hardness level before buying a water softener system is essential. It’s just not some random number you can guess. You must know the water’s hardness.

Because when it’s time to program your water softener, the softener will ask you to type in the hardness number. So having the correct number is essential so the water softener can work effectively.

So you have to test your water, which can be done locally in most cases. But if you can’t find anyone, you can always send a water sample to a company that checks the levels. But the best way would be to use a simple water test kit. Because you can test it multiple times, it will also cost you less.

If you’re connected to the city water, contact your local water utility and ask them for the hardness value.

If you have a well, you must test your water hardness and iron levels.

The hardness value must be corrected if iron is in the water. For every 1.0 ppm of iron or mg/L of iron, 3 GPG of hardness must be added to the total hardness value.

Grains per Gallon (GPG)

Parts per Million (PPM) & mg/L

Soft<10 – 17
Slightly Hard
1.5 – 517 – 60
Moderately Hard
3.5 – 760 – 120
Hard7 – 10120 – 180
Extremely Hard >10>180
Hardness Chart

Water Consumption

The next step is to find your daily water usage by checking your water bill. The bill will show you the total amount for the month, so you will have to divide it by 30 to get a rough estimate.

This goes for all the water you’re using in your household.

If you can’t find this information, use this formula: [ number of people in your household ] x 75 gallons = How much water you use daily.

75 gallons is what the average person uses every day and is also the industry standard measure.

Read also: Will Water Softener Water Kill Plants?

Calculating Your Daily Softening Needs

To get the correct size of water softener, you must know your softening requirements. Let’s use this example:

A household of 4 people, now we use the formula from above:

4 people x 75 gallons = 300 gallons of water / day

Let’s assume that the water hardness is 10 grains per gallon.

Now we multiply those numbers. So 300 x 10 grains per gallon x 300 gallons of water = 3000 grains / day.

That means the softener will remove 3000 grains per day in this example. But you also need to have the regeneration process in mind, which it does about once per week, so you need a water softener that effectively removes 3000 x 7 = 21,000 grains of hardness.

Look at our article: How often should my water softener regenerate, to get a deeper understanding of that process.

If iron is present in your water, add 5 grains of hardness for every 1 ppm of iron.

Choosing The Right Type Of Water Softener

So by now, you’re probably wondering, “What size water softener do I need.” Soon you’ll know.

When sizing a water softener, you need to take a look at capacity and efficiency. Let me explain why.

Water Softener Capacity

A water softener’s capacity is the amount of hardness it can remove before it needs to do its regeneration cycle.

Enough capacity is essential to getting the desired results, which is “soft water.”

Let’s continue with the example above. We need a water softener of 21,000 in total softening capacity.

At this step, many online stores will give you the wrong answer.

Most softeners come in the capacity of:

  • 24,000
  • 32,000
  • 48,000
  • 64,000

When looking, the 21,000-grain system seems like a good option, but the sellers don’t tell you that it takes a lot of salt to regenerate this system. It can do the job, but it would cost the user much salt to achieve this.

What you should take a look at is the cubic foot of resin. It’s the amount of resin a system contains. For example, a system with 24,000 grains would go under 0.75 cubic feet, and 32,000 grains would go as 1 cubic foot.

Cubic Feet of Softener ResinGrains Capacity
The chart over cubic feet of softener resin and the capacity

So if we take a look at salt consumption:

A 24,000-grain system would need 27 pounds of salt to regenerate.

A 32,000-grain system would need 36 pounds of salt t regenerate.

But they don’t tell you that if you use 6 pounds of salt to regenerate a 32,000-grain system “one cubic foot,” it would get a 20,000-grain softening capacity.

If you compare these systems’ costs, one cubic foot would be more expensive, but the saving you would make from all the salt would be worth it.

Read also: How To Add Salt To Water Softener

Water Softener Sizing Chart Based On People In Your Household

Hardness (GPG)1 to 2 people3 to 4 people5 to 6 people7 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
Grain Chart

Read also: 9 Reasons Why Your Softened Water Tastes Salty

“So what size water softener do I need?”

So when deciding what kind of water softener you should buy, you need to look over the hardness of your water and your water consumption.

Only then can you decide what water softener you should buy.

Good luck in finding the correct size of water softener just for you!