It's around this time of year that I watch the TDS of my RO unit drop. I'm talking about the output of the RO system before the DI stage. Whenever I turn on the RO/DI system, which is twice a week, I open a valve before the DI stage and let it run for 90 seconds. By avoiding TDS creep, DI resin lasts longer. Link: http://www.reefaddicts.com/content.p...thy-of-concern Once the water is flowing, I'll turn on the TDS meter to observe the numbers ...