TCEQ Class D Water Operator License Practice Exam 2025 – Complete Study Resource

The minimum chlorine dosage for disinfecting a new main before it is put into service is 50 mg/L. This figure is established to ensure that adequate disinfection occurs, effectively eliminating harmful pathogens and contaminants from within the newly installed main. The dosage is critical as it provides a safety margin to ensure that even if some chlorine is consumed by organic matter or biofilms within the pipe, there will still be enough residual to achieve full disinfection.

Setting the minimum at this level is based on standards and guidelines recommended by health and environmental protection agencies, ensuring public water safety. A dosage of 50 mg/L is recognized as sufficient for achieving a thorough disinfection, allowing the water to be safe for consumption and use once the main is put into service. Lower dosages may not guarantee complete eradication of microorganisms, while higher dosages, though sometimes used, can lead to other concerns such as corrosion or taste issues if left in the system.