I changed the sediment filter and carbon on my RO/DI unit recently, and I’m always amazed at how gross they can get. These are the cheapest cartridges in the water filtration sequence, about half the cost of DI resin or an RO membrane. Looking at the state of this filter, I know I definitely should do it more often. While it is usually recommended to replace these every 4 to 6 months, I had let mine go 8 months since I don’t go through very much water. Yuck!
The carbon filter was less obvious visually, but because they protect the RO membrane from chlorine damage, I like to change it whenever I do the sediment filter. Also, remember that the micron rating on the sediment filter should be at least as fine as the rating of the carbon.
After I made the change, water pressure coming into the membrane went up instantly, and production of filtered water accelerated. Thanks to the in-line TDS monitors on my Spectrapure unit, I also notice that water coming out of the first two stages and coming out of the RO stage is lower in TDS than before. And, this will also further the life of the expensive DI resins, which equates to additional cost savings.
Maybe most exciting, my wife claimed to notice a sudden difference in the taste of our drinking water (we get that out of the RO stage but before the DI). She even brought this up without me telling her I’d made the change. This ancillary benefit helps with continuing efforts to keep my spouse on board with the two reef aquariums in the living room, which is, of course, always day-to-day.