Well I tested the product water on our desalinator and TDS is at about 300ppm. This is fine for drinking water but clearly not for top-up. I guess that's the tradeoff for producing 58 gal/hr! Granted that 300ppm could be full of useful stuff since it is derived from fresh sea water, but I don't think it's worth the risk. When I get my test kits I will certainly test to see what's in there just out of curiosity. I have added an AquaFX Octopus to my order (luckily I don't think it has shipped yet). I picked it because it has a 1:1 wastewater ratio. There is no city water here and all of our fresh water is rain water fed into a cistern. The fiancee will like my aquarium even less if I run that dry. The upside is that I can run a tee off the membrane for drinking water, saving cost at the grocery store. I will also feed the waste water to the washing machine creating almost zero waste. I also measured the TDS in the cistern water and it is around 50ppm so I don't imagine the RO/DI will have to work too hard. Obviously there shouldn't be any chloramines in there so it should be mainly organics that get filtered out.