Arizona Plumbing Practice Exam

A section of the water main pipe has been required to be back in operation within 12 hours. The section shall be filled with a water/chlorine solution containing how many parts per million of chlorine?

1. 100

2. 200

3. 300

4. 400

The correct answer is: 200

In the context of water main repair and disinfection procedures, the requirement for a water/chlorine solution is critical in ensuring that any potential pathogens are eliminated before the system is placed back in service. The appropriate concentration for disinfection typically follows standards set by health and safety guidelines. A chlorine concentration of 200 parts per million (ppm) is the standard recognized by various health and plumbing codes for the disinfection of water mains. This level of chlorine is effective at killing bacteria and viruses, while also being safe enough for short-term exposure in municipal water systems. Ensuring the required concentration is maintained during the fill is crucial to achieving complete disinfection before the reactivation of the water supply. Concentrations higher than 200 ppm may be unnecessarily harsh for this application, potentially leading to unpleasant tastes or odors in the water, and could also require more extensive flushing and neutralization efforts after disinfection. Consequently, the 200 ppm solution strikes an optimal balance between effective disinfection and operational viability.