Industrial Water Softener Sizing & Application – Hardness Leakage

What is industrial water softener hardness end-point leakage? That is the amount of hardness expressed as grains per gallon (gpg) or parts per million (ppm, mg/L) present in the effluent water at the point when a run is terminated. This phenomenon is graphically shown in the figure below (The Continuous Hardness Leakage Chart).

Continuous Hardness Leakage Chart

Please note that hardness leakage information below provides general guidance, but an on-site engineering industrial water softener analysis is usually advised to determine the most cost-effective next steps. You will also find the Industrial Water Softener Application Sizing Guide – Resin Exchange Zone resource to be helpful. Also see our industrial water softener hardness monitors and analyzers.

An increase in hardness is noticed in the softened water when the Active Exchange Zone reaches the lowest point of the water softener resin bed. The run can be terminated or continued until the hardness ions increase. The hardness increase or breakthrough is gradual at first followed by a sharp increase after the water reaches 17.1 ppm (1.0 GPG ). Approximately 15 % of the total useable throughput occurs during the softener end-point range.

Industrial water softener hardness leakage is the release of hardness ions during the service run. The degree of hardness leakage is directly related to the amount of Total Dissolved Solids (TDS) (also see our Total Hardness Calculator) present in the raw water and the amount of salt used to regenerate the resin (salt dosage). Standard industrial water softener salt dosing is 15 lbs of salt per cubic foot.  This yields 30,000 grains of capacity per cubic foot and has minimal hardness leakage.  A more efficient salt ratio of 6 lbs per cubic foot of resin will be up to 40% more efficient from a salt consumption perspective but will have more hardness leakage.

Hardness ions in the water left in the bed after regeneration causes hardness leakage. These hardness ions are bombarded by the sodium in the soft water during the service run. The sodium ions have a regenerating effect on the remaining hardness, causing hardness to enter the soft water as hardness leakage.

Continuous hardness leakage is an average of hardness leakage during the operating run, but does not including the normal rise in hardness at the end of the service run. At the beginning of the run, leakage is greatest because the sodium-rich soft water is “regenerating off” all the hardness left at the very bottom of the bed. As the run continues, this hardness at the bottom is eventually displaced with sodium. Therefore, the hardness leakage is greater at the beginning of the run and less just before final breakthrough.

industrial water softener end-point leakage is the amount of hardness present in the effluent water at the point where a run is terminated. The run may be terminated at any point during the “EL” End-Point Range.


Also see the industrial water technical articles and resources helpful, along with our industrial water softeners information.

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