I have my RO/DI unit under my sink upstairs -- the waste water goes right back into the drain (I'm not a plumber either and it was easy). I got mine from airwaterice.com and I think its a 3 to 1 waste to good water. Mine came with a 3 gallon holding tank with a drinking water nozzle put in the sink as our TDS in our drinking water was like 850. The RO takes it to around 40 - 60 and the DI portion for the reef tank takes it down to 2-8. The holding tank is for drinking water only and the rest I let run into a 5 gallon bucket for a 2-4 hours and thats enough water for 2-3 days for me. A little bit of a pain but I drink healthier as well. Oh ...... don't forget about the water running into the bucket and go to sleep, have a wet floor in the morning if you do 
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90 gallon with 26 gallon sump/refugium, 2 x 250 MH lighting, 100lbs live rock, 1 - yellow tang,1 damsel, 1 - cleaner shrimp, 1 - coral banded shrimp, 3 - emerald crabs, 2 - porcelin crabs, 6 - peppermint shrimp, 1 - green ricordia, 1 - toadstool, 1 - brittle starfish, 1 - sand sifting star, 100's baby feather dusters,Ass mushrooms, frogspawn, xenia, 1 clam,
6 - Leather coral, Green star polyps,Lime green/orange button polyps,1 huge carpet anenome,various snails/hermit crabs |