What RO/DI Unit?

[Myka]

I use the AquaFX Barracuda 4 stage 50 gpd RO/DI unit. My tap water is 50 psi and 92 tds, I get 1 ppm tds out of the RO cartridge, and 0 tds out of the DI cartridge.

Filmtec 50 gpd = 98% rejection rate
Filmtec 75 gpd = 98%
Filmtec 100 gpd = 90%
BFS 150 gpd = 98%

Which means that if you have a 100 gpd unit your DI resin will burn out quicker since the rejection rate is 90%.

From what I understand, a typical unit will have a 4:1 waste water production. I haven't measured mine, but that seems about right.