After a new water main is installed and pressure tested, what is the required disinfection procedure before flushing?

Filling a newly installed water main with a chlorine solution of 25ppm to 50ppm free chlorine is essential for disinfection as it effectively eliminates harmful bacteria and pathogens that may have entered the pipe during installation. This process is known as chlorination and is a crucial step in ensuring the safety and quality of drinking water.

The concentration range specified (25ppm to 50ppm) is sufficient to achieve a strong antimicrobial effect without damaging the pipe material. Once the chlorinated water has been in contact with the pipe for the appropriate amount of time, it can safely be flushed out, ensuring that any residual chlorine levels are within acceptable standards before the water is released into the distribution system for public use.

This disinfection procedure is a standard practice to maintain public health and complies with regulatory requirements. Other methods listed, such as flushing with clean water for 24 hours or filling with clean water for 5 days, do not provide the necessary microbial control and could leave the system vulnerable to contamination. Photographic mapping, while beneficial for maintenance and record-keeping, does not serve any role in the disinfection process.