Fleck 9100SXT Dual tank water softener

How to Size a Water Softener: The Definite Guide

There are so many water softeners being sold online and also in stores around us. However, having just any water softener is not the goal. You need to buy the right size to ensure you get the best for your buck. The internet is filled with sizing charts that tell you the size of water softener to invest in. However, this information does not take into account salt usage during the process. You need to invest in a system that is efficient in that, the size is right and salt usage is at its lowest. It completely beats the purpose when you get the right size and yet incur more costs while softening your water. A proper system should match your specific water quality while minimizing salt use and maximizing soft water capacity.

Fleck 9100SXT Dual tank water softener


Effective ways to size your water softener

To effectively determine the right size you need, you have to calculate your daily softening requirements. This information will be derived from calculating your water hardness level and water consumption.

Water Hardness

This refers to water containing dissolved hard minerals above 1 GPG. The minerals mostly include calcium and magnesium.

Measuring of water hardness is done using testers that report in grains per gallon, milligrams per liter(mg/L) or parts per million.

The standard way to discuss water hardness is grains per gallon (GPG) which means that one grain of water hardness is equivalent to a 1/7000th of a pound. When measured in parts per million(PPM), then one PPM basically means out of one million units, one unit is a hard water mineral.

When water hardness is measured either in PPM or mg/L dividing it by 17.1 will convert the results to GPG.

It is also important to note that if your water has iron then the water hardness value must be adjusted. For every 1.0 mg/L or PPM, 3 GPG of hardness needs to be added to the total hardness value.

Having your water hardness measured and getting the right values is very important. Avoid guessing these numbers because it will result in an improperly sized system. Getting these values is also important because you will need to key them in when programming your water softener.

Water consumption

The best way to measure your households water usage is by metering. Luckily the water department does this for you and provides with a water bill each month. With the total consumption listed in the bill, you can figure out how much water you use in a day on average. This may not be the exact value for each day but it will do.

If you do not have access to this information, you can use other methods of measuring water usage. You could also just take the number of people living in your house and multiply by 75 gallons. This will give you a rough estimate of your daily water needs.

Calculate Daily Water Softening Requirements

Multiply your water hardness values by your daily water use. This will give you the daily softening requirements that your softener needs to complete.

For example;

If your water hardness is 10 GPG

Daily water use: 4 people X 75 gallons of water= 300

Daily water softening requirements= 10 X 300=3000 grains per day

So with this, your water softener is required to remove 3000 grains per day

Choosing the right water softener

Now that you know what your daily softening requirements are, its time to figure out which water softener will match your conditions.

When getting your water softener it is important to check water softener reviews and note that it is sized so that it can regenerate about once a week. This period ensures that the resin bed is kept fresh and the water valve is not worn out.

Keeping in mind the regeneration period, you also have to factor in salt usage. Given that your daily softening requirements are about 3,000 grains multiply by 7 days before regeneration. This gives you 21,000 grains of total water softening capacity.

Now that you have this figure, you’ll find many recommendations on the internet that you would be tempted to go with the closest number to your current figure, However, this is not the way to do it.

What the information on the internet does not take into account is the salt used during regeneration. With a 24,000 grain system ( which is the closest value) it takes 27 pounds of salt to fully regenerate the system.

However, if you use a 32000-grain system programmed at a salt setting of 18.5 pounds, you get 1729 grains per pound of salt. By programming this water softener to a capacity of 21000 grains and a salt setting of 6 pounds of salt, you get 3500 grains per pound of salt which doubles the effectiveness of your water softener.

Given that it would be priced higher compared to a 24000-grain system, the salt usage and efficiency would far outweigh it and make up for the cost difference.

Having all this in mind, here is a list of capacity options with the peak and efficiency levels included.

  1. 1.0 cubic foot of resin – 32,000-grain peak, 24,000 efficient e.g the Morton MSD34C
  2. 1.5 cubic feet of resin – 48,000-grain peak, 32,000 efficient e.g the Fleck 5600SXT
  3. 2.0 cubic feet of resin – 64,000-grain peak, 40,000 efficient e.g the Nuvo H2O


It is very clear that you have to take your time and really understand all the factors that go into getting an efficient water softener. Having all the facts will help you base your decision on what will work for you best and not what’s on the internet. By now you know the benefits of having the right water softener in terms of size, type, and efficiency. Always keep that in mind and don’t get sidetracked by the many promises a company may make about the performance of their product. With all this, you can get to finding the right fit for you and enjoy the outcome of having an efficient water softener.

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