Which line is used to take samples for testing from the water softener?

The water softener sample line is specifically designed for taking water samples from the water softener system. This line is integral for testing the quality of water produced by the softener, assessing its effectiveness in removing hardness and other impurities. Regular sampling from this line allows operators to monitor the softening process and make necessary adjustments or maintenance decisions based on the test results. The other lines mentioned serve different functions; for example, the condensate tank line is primarily related to the collection of condensate, the make-up water line deals with filling systems with water, and the heat exchanger line is focused on transferring thermal energy. Thus, the distinct purpose of the water softener sample line makes it the correct choice for sampling in this context.