Just a little background my 4 stage BRS RO/DI filter has got to be at least 3 years old. All 3 filters were replaced maybe 3 months ago. (DI resin, carbon block, sediment filter) I usually only make about 15 gallons every 3 weeks or so. The DI resin I have changes color when it becomes exhausted and it's still looks brand new. Today while I was making water I checked the TDS and it was at 7. Assuming the unit is working properly and the filters are relatively new, could the high TDS be due to an old membrane? Thanks.
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