Recommend a RO/DI system to me

[Myka]

Oh my Brett, I hope they aren't in that order!

It all starts out with a TDS meter, go buy one ($15-30+) and test your tap water after allowing it to run on cold for a few minutes. You want fresh water, not stuff that's be sitting in the pipes for a day. If your TDS is around 300 ppm or less you can easily go with a 4 stage. If you have a lot of solids in the water that settle out when you pour a glass/bucket of water you may want to use two sediment filters.

Basic system is 5 micron sediment filter, 1 or 5 micron carbon filter, RO membrane, DI resin.

I would suggest you use either a 50, 75, or 150 gpd system and not a 100 gpd as the RO membranes are not as efficient and you will burn through DI resin. Pick an RO membrane that is 98% rejection (that's efficiency). That means if your TDS is at 200 ppm it will be at 4 ppm when it comes out of the RO, and the DI will take it down the last 4 ppm. DI will take out up to 20 ppm, but you will burn through it real fast.

Bulk Reef Supply makes great RO systems, including the build your own ones.