From which port is the first total chlorine sample taken?

The first total chlorine sample is taken from the 1st post carbon tank because this is where chlorine levels are most relevant for evaluating the effectiveness of the carbon filtration process in removing chlorine from the water. After water passes through the reverse osmosis (RO) system, it generally has very low chlorine levels. The carbon tank serves to adsorb chlorine and other contaminants, making it crucial to monitor chlorine levels at this point.

Taking the sample from the 1st post carbon tank allows for an accurate assessment of how effectively the carbon tank has reduced the chlorine concentration from the water. This sampling point is representative of the water's quality directly after treatment, which helps determine if the filtration system is functioning properly and meeting required standards for chlorine levels before the water continues to subsequent stages of treatment or distribution.

In contrast, sampling from other locations like the post RO, pre-carbon tank, or post GAC filter would not provide the same insights into the carbon tank's performance or give an accurate reflection of chlorine residuals after carbon treatment.