Not necessarily bad if brown. My gets brown after 2 months or so and I change every 6 months. It should read 0ppm. Although RO
only can have a reading of some ppm
since only takes out percentage of supply water. Get a in-line tds
meter. Check out "the filter guys". Might not be a bad idea to add a DI
will always give you 0ppm. Best for aquariums.