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Removing some of the water of a system periodically or continuously, and replacing it with fresh water, to control the continuous accumulation of dissolved solids in the water (WHO 2006).See Bleed-off


This process of blow-down may be controlled by a conductivity controller that detects the increase in conductivity due to the dissolved solids, and automatically regulates the rate to hold a preset conductivity by triggering the operation of a solenoid drain valve.Blow-down may be activated immediately before the addition of the biocide, to ensure that the amount of suspended dirt in the water that might react with and neutralize the biocide is minimized. Blow-down may then be stopped for a period after the addition of the biocide, to ensure that the chemical is retained at a sufficient concentration for long enough to be effective. (WHO 2006)

References and Links

WHO (2006) Legionella and the prevention of legionellosis

WHO Lexicon page (translations and examples)

Other Definitions


See also


External Resources

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