At what ppm tds do you change out your RO membranes?
Personally, once my RO hits 15 ppm tds I change it out. It’s cheaper to change my RO membrane out yearly than to change my DI multiple times per month during busy season. I get my membranes from a friend who own a large industrial water filtration supply company.
For the first 6 months I use RO only with no DI, getting 000-003 ppm tds. Once it goes higher I use DI to polish things off.
What’s your RO tds ppm threshold?