What'd you'd be making is called a camper/rv filter.You could make a homemade filter out of just carbon and it would filter the water. Im sure there are diy ideas all over the web for homemade filters, i dont think one the size a water bottle would have much filtering capacity.
The waste is insane to achieve 0 ppm. I don't see the point of ro unless your water is really bad.Bought one of those RO Britta systems for under the sink. Make sure you get one that produces a lot of water a day. Took all day to get 6 gallons. Beautiful water though with 0 dissolved solids and we live in Nevada!
My ro system was also under 200$ w replacement filters costing 90$ for 5 months usage...damn i thought mine was slow at 35g a day but it does the jobWe have some of the worst water in the country. It was only $199
I'm using DWC.My ro system was also under 200$ w replacement filters costing 90$ for 5 months usage...damn i thought mine was slow at 35g a day but it does the job