How long should the RO operate before collecting pre-treatment water samples for chlorine testing?

The correct answer is based on the recommendation that reverse osmosis (RO) systems should operate for a minimum of 15 minutes before collecting pre-treatment water samples for chlorine testing. This duration allows for the stabilization of the system and ensures that any chlorine present in the water is adequately mixed and represented in the sample.

Collecting samples too soon after initiating the RO process may not accurately reflect the actual chlorine levels because the water has not yet equilibrated within the system. By allowing the RO to operate for at least 15 minutes, any fluctuations in chlorine concentration due to initial system dynamics are minimized, leading to a more reliable assessment of the water quality prior to treatment. Thus, this practice is crucial for ensuring effective monitoring and maintaining the integrity of the water treatment process.