I've run into my first customer with significant tds. I believe the last two companies I worked for were not approaching these situations correctly, so I'm looking for some input. His TDS is 1640 at the tap with softened water feeding, (what will be) an under sink (POU) RO. the water temperature is around 45+- degrees and PT at 40/60 with 3 people in the home (which equals around 9 gallons of RO water use per day). Would you recommend a 50gpd RO with a booster pump or can I get by with a 100gpd membrane.