By the way, Jeff - the dual TDS meter is a great investment, takes the guesswork out of when its time to replace the DI media and filter cartridges in the RO unit.
For example, for the past couple months my setup runs about 160 PPM into and 0 PPM out of the RO/DI unit. I checked it yesterday and its running 14 PPM out. So I know the DI is getting exhausted. My target for product water is 0 total dissolved solids out of the units. I check the TDS at least once or twice per week to catch it early. This keeps algae from blooming and coral health & growth maximized.
I also run a pressure gauge coming out of the unit, though thats not necessary. And I also run an auto shutoff valve to relieve pressure on the membrane when there's no demand. This gives it a better lifespan. And of course, checkvalves in a couple places. I have a flush kit as well but dont use it, though I probably should.
