AWWA C651-14 DISINFECTING WATER MAINS

This standard presents essential procedures for the disinfection of new and repaired potable water mains. Topics covered include forms of chlorine disinfection, a description of the disinfection procedure, preventive and corrective measures during construction, methods of chlorination, final flushing, bacteriological testing, redisinfection, final connections to existing mains, disinfection procedures when cutting into or repairing existing mains, and special procedures for caulked tapping sleeves. Appendixes cover chlorine residual testing, chlorine dosages, and disposal of heavily chlorinated water.

Major revisions made to the standard in this edition include the following:

• Expanded guidance for disinfecting existing water mains after repair. This includes a rationale for evaluating risk during pipe repairs, and the level of disinfection and sampling needed under each of those conditions. The revision also clarifies differences in the requirements between new and repaired mains.
• Added a spray disinfection method for large transmission mains.
• Changed the requirement for bacteriological sampling in new mains from two sets of samples 24 hours apart to add two options for two sets of samples: Option A samples are 16 hours apart and Option B samples are 15 minutes apart after a 16 hour rest period.
• The flushing rate of 2.5 ft/sec has been increased to 3.0 ft/sec for a scour flush based on testing performed under recent studies.
• References to new standard ANSI/AWWA C655 are included for dechlorination and disposing of heavily chlorinated water.

The update takes into account the findings from a recent project from the Water Research Foundation (Project No. 4307, Effective Microbial Control Strategies for Main Breaks and Depressurization).