How to Calculate Resin Capacity for Softener | Softening Plant?

Before to Calculate the capacity of the Water Softener (softening) Plant,  to choose how much water to be softened. In this case, 100M3 to be softened at 400 ppm of Feed Hardness to 5 ppm.

How to Calculate the resin capacity?

The Resin Exchange Capacity is mention into the product’s supplier Data Sheet*.

Normally cationic exchange capacity : 55/liter of resin.

Hence, Liter of resin = (Feed Hardness in ppm X Water Qty M3) / Exchange capacity

= (400 x 100 / 55) = 727 liter resin sufficient


How to Calculate Salt Quantity?

= 110 Kg NaCl { ? 150 Gram NaCl / liter of resin)

so quantity of water require to dilute @100% solution

= say 344 Liter Water { ? 320 Gram NaCl @ 20Deg C / liter of Water )

to get 10 % solution add 3440 liter of water

Now 3784 liter is having for regeneration and that much of water to be injected 20 Minute

then start backwash process to another 40 minute

after that fast rinse until get hardness is < 5 ppm once it is reached now the plant is ready to start the process, it can extract up to 100 m3

Feed pressure to be maintained up1.5 – 2 Bar,

*Resign exchange capacity is important, it is vary product to product.

Article by Sivanandan



  1. Sphinx says:

    How to Calculate Salt Quantity?

    = 150 Kg NaCl { ? 150 Gram NaCl / liter of resin)

    Is the above calcualtion wrong?
    150 Gram NaCl x 727 = 109.05 Kgs of NaCl

    Please correct me if I am wrong.

  2. Sphinx says:

    Also please let me know what is the purity of NaCL you have considered in the above calculation

  3. For good knowlege this material is good.

  4. Asad says:

    Dear sir
    Your information more help full to take knowledge.

  5. Jerry says:

    please wats the best approach to this design question

    Design a water softening plant for a water work having the following data:
    Hardness of water= 450 mg/liter as CaCo3
    Available hardness after treatment = 50 mg/liter as CaCo3
    Quantity of water to be treated = 25000 liter/ hour
    Ion exchange capacity of resin to be used in the plant = 10 kg of hardness / cub.m
    Salt required for regeneration of resin= 45 kg/ cub.m of the resin
    The water softening plant works 2 shifts of 8 hours per day. Assume any suitable data where necessary.

    thank u

  6. Navin says:

    What would be the efficiency of hardness removal we could expect? From say 800 ppm by this method how much hardness can we remove and what would be left?

  7. yethiraj says:

    WHAT IS THE PRESSURE DROP FOR USING 1000 LPH SOFTENER BY USING 10X54(Dia. x Height) with multiport valve. eg. inlet pressure is 2 kg / cm square, what is the output pressure after softening

  8. nitesh says:

    how to calculate the hypo dosing in wtp?????

  9. Mitang Patel says:

    What would be the efficiency of hardness removal we could expect? From say 800 ppm by this method how much hardness can we remove and what would be left?

    • Mitang Patel says:

      our flow rate 30 m3/hr and Hardness calculate for resin is 320 ppm. But inlet hardness is vary from 250 ppm to 700 ppm and we use the softener vessels is 48×72 and resin qty is 1210 ltr. and our Obr is 200 m3/ hr. so after regeneration we got hardness only 20 ppm but party required less than 5 ppm so, what we do.

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