They're all the same size, except they have a different number of stages. So a 2 stage would be smaller than a 4 stage. Make sure you buy a 4 stage or better for SW. I wouldn't get anything slower than 50 gpd because it's painfully slow!! You can find them new for about $175-225. Used you should be able to find for about $100, BUT beware because often on used ones, or ones that haven't been used for a long time, the cartridges need to be replaced, and they are the expensive part! Check out J&L's pricing for units and cartridges.
I have this unit:
http://www.jlaquatics.com/phpstore/s...t_ID=ro-afb050 When I bought it, it was $189 last December. Price sure went up a lot.
Here's a price list from J&L:
1 micron (1st stage) - $7.45
Carbon block (2nd stage) - $13.95
50 gpd RO membrane [for my unit] (third stage) - $79.95
Mixed resin DI cartridge (fourth stage) - $31.95
Total - $133.30 +taxes
So keep that in mind if you're buying used.
