Understand Water Softener Resin Capacity for Best Selection

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The key function of a water softener is eliminating hardness in raw water to soften water for drinking and other residential & commercial purposes.

A water softener’s capacity can be defined as the amount of water hardness removed between regeneration processes. The title of water softener capacity is poorly understood by both dealers and the consumers within the field. This article will help you to have simple theories of water softener capacities.

Do you know how a water softener mentioned its capacity?

Most websites describe water softeners by their grain capacity. But another way of measuring softener capacity is galloons. You might have seen that it is mentioned 24000, 32000, 48000, and 64000-grain water softeners in websites. Most regularly, a 32000-grain system contains 01 cubic foot of resins. So, a system with 32000 grains should trap 32000 calcium and magnesium compounds in water. But this is not practical in the field because the above results can obtain only under controlled conditions such as temperature and pressure in the laboratory. Therefore, you can understand that a water softener with 32000 grains cannot eliminate its total capacity but 28000 – 30000. Water softener grain capacity is directly affected by the amount of salt required for regeneration. The grain capacity can be interpreted as the weight of calcium and magnesium ions removed from hard water before regeneration.

Do you know about the following factors?

Some factors need to pay your attention to when considering water softener capacity.

  1. Water hardness
  2. Flow rates
  3. Water capacity
  4. Regeneration frequency
  5. Resin capacity

Water hardness

Water hardness can interpret as the amount of dissolved Calcium ions and Magnesium ions in your water. The water hardness is a measure of grains per gallon (gpg). Also, water hardness can measure in milligrams per Liter (mg/L) or parts per million (ppm).

01 grain of hardness = 1/7000 pounds of dissolved Ca & Mg.

1 gpg = 17.1 ppm = 17.1 mg/L

If you purchase a water softener, the most important point to know is the total water hardness of your water. You must test your water quality if you are on your well water or request a water quality report from your water supplier. Check whether there is iron in considering level; it is recommended to re-correct the total hardness value. For every 01 ppm of iron, add 03 gpg of hardness to the total value.

Conversion of mg/L to gpg =

Water Capacity

In other words, this is the daily water consumption for your purposes. It can be residential or commercial. If you are using municipal water, you can get accurate data from the water bill or flow meter data. But for residential purposes, if you use your well water, you can have a reasonably accurate capacity by multiplying the number of family members by 75 gallons per day per person (75 gpd/person). Take your national average water consumption for calculation for the above.  

Flow Rates

If you select a system with a small capacity than actual water consumption, there will be a large water pressure drop, which can be increased with no iron calculation. The combination of the internal diameter of valves, mineral tank, distribution system, and volume & the type of ion exchange resin helps determine the flow rate of a well-engineered softener. 

Resin capacity and the type

The main component in a water softener is resin in the vessel. Resins are tiny polymer beads with Na ions bonded with electrostatic bonds. They exchange their Sodium ions with Ca2+, Mg2+ ions in raw water and release sodium ions into the water. Resin bed can be saturated with these Ca2+ and Mg2+ ions, therefore a regeneration process.

Resin capacity or system capacity is defined as the amount of resin within the softener vessel. As mentioned in the above paragraph, 01 cubic foot of resins can remove approximately 28000 – 30000 grains of dissolved hard water ions. If your system is 01 ft3 in capacity, it will saturate with 30000 grains of hard water minerals. Now, it requires a regeneration process to reactivate the resin bed.

Regeneration Frequency

A well-engineered water softener has enough capacity to tolerate its feed water. But, an undersized water softener often requires regeneration processes and its mechanical components. The undersized softener can result in more salt consumption, power, and a short life span of resins. An accurately designed water softener must have enough capacity for the best time gaps for regeneration processes. 

Can you calculate the daily softening requirement for residential purposes?

Hardness in ppm = 160 ppm

Hardness in grains per gallon (gpg) =  

Daily water consumption in gallons per day (gpd) = 4 family members x 75 gpd

  = 300 gpd

Daily softening requirement = 10 gpg x 300 gpd 

 = 3000 grains per day

In this example, you require a softener that can remove 3000 grains per day, and a softener can size to regenerate once a week. Why once a week regeneration is good? Actually, a regeneration process depends on many points, but we can understand that it depends on water hardness. But usually, it is about once a week. The regeneration process needs approximately 50 gallons of water. So, water consumption will be low. Also, keeping the balance between resin bed freshness reduces the tiredness of valves and protects them from wear and tear. 

Assuming the regeneration process occurs once a week; 

Required water softener capacity = 3000 grains per day x 7 days

= 2100 grains per week

That means your softener wants 21000 grains of total hardness to regenerate once a week. Assume; there is no iron or manganese in your water. 

What will be the best softener to select?

You know, there are various grain capacities water softeners in the market. It can be 24000, 32000, 48000, and 64000. At a glance, you will select; 24000 one is good for mine because my calculation brings me 21000. Is it correct? Think a little more now. A 24000-grain system includes 0.75 m3 of resins inside the vessel. Yeah, it is true; a 24000 softener can grab 21000 grains in your water, but the salt usage is too high. But if you can go for 32,000 systems, it contains 1 m3 of resins and uses a meager salt amount. This salt gap can cover the price gap of these two systems, and durability is pretty good with a higher capacity one. This will helps to less salt to buy, less salt to shortages, and less salt to discharge into the environment.

Can you aware of this? 

When you buy a softener, you must have the basic idea of the above points. This will guide you to understand what your dealer informs about his production. You can compare and will be able to select the best that satisfy your requirement. Always go for minimized salt capacities that meet your goals. Salt efficiency always shows how much salt will be used and how much softening capacity results from the system. Discuss with your seller, and have reference manuals, graphs, and charts to be thorough with your product.


Water softeners capacities are available in grains per gallon at the market.

Grain capacities express how much hardness can remove in water up to regeneration.

Water softener capacities are directly combined with salt efficiency: water hardness, Flow rate, resin capacity, regeneration frequency, and water capacity. 

Always strictly adhere to the dealers’ guides with your knowledge gained with the site, select the best softener which reduces salt consumption and completely softens your water up to the required rate.


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