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News & Press: Illinois Section AWWA News

Updated Regulations on Chlorine Residual

Tuesday, October 1, 2019  
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“Effective July 26, 2019, the Part 602 regulations regarding new construction sample requirements have changed. The “no bacterial growth” requirement has been removed. The new requirement is two satisfactory sample sets that show the absence of coliform bacteria and the presence of a minimum chlorine residual when required.  For future projects, please comply with the updated Illinois Administrative Code, Title 35, Section 602.310 requirements.”

Just to run through that, before we required membrane filtration showing no presence with a minimum of 1 sample per 1200 feet for water mains with at least a 0.2 ppm free residual or 0.5 combined. Now we are transitioning to requiring colilert with two samples at least 24 hours apart per 1200 feet for water mains with no colonies and a minimum 0.5 ppm free residual, or 1.0 combined. We currently accept both methods for now, but prefer everyone to start using colilert for operating permits.

Also here's a link to  updated regulations with the part for distribution systems found under 604.


Section 604.725 Residual Chlorine

a) A minimum free chlorine residual of 0.5 mg/L or a minimum combined chlorine residual of 1.0 mg/L must be maintained in all active parts of the distribution system at all times.

b) Community water supplies must monitor chlorine residual to determine the amount and type of residuals existing at different points in the distribution system.

c) Community water supplies must not mix water sources with free chlorine and combined chlorine residual.


Thanks to Dan from our Education Committee for this information!


To learn more about new and upcoming Illinois regulations - register to attend the ISAWWA Regulatory Update on October 24, 2019.


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