My tap TDS is 560-800, my RO only TDS is between 2 and 3. I replace the sediment and carbon every 12-18 months based on headloss and chlorine breakthru and DI lasts a year on the MaxCap and 3 years on the SilicaBuster. That's with a 100g display with 30g sump and a 16g nano in Phoenix with high evaporation. You figure out which system is more efficient and costs less to own. The portables are not the way to go.