as a matter of fact, i just changed my filters yesterday..... right after installation (about 3 o'clock) my TDS meter read 19ppm(my tap is only 35). At about 6:30 TDS read 5ppm. At 10, 2ppm. Finally, at midnight(or around there) TDS read 0.... so id give it at least a half a day or so....oh yeah, and i had already flushed the new filters prior to installation....