And realize that unless you have conditions that match the membrane spec's, you won't actually get the full 75 gpd for instance, out of a 75 gpd membrane.
I would shy away from most RODI that state 100GPD or more. they tipicly have a low rejection rates, 90% . The standard 75GPD have 96-98% rejection rate which is good.
I meant, I thought the same thing, after I flushed about 5 gallon through it I used a TDS meter and I am getting 0 tds water out of the unit, I'm also only getting about 80gpd out of mine since I only have 60psi going into it