RO filter replacement schedule?

[Subrosa]

Not sure what Ray's unit comes with, but an inline tds monitor is an easy and inexpensive way to know precisely what condition your membrane is in at any time. Units are available with multiple channels, to allow monitoring of the feed water, the water exiting the membrane before it enters the deionizer chamber, and the finished product water at the slide of a switch. An inline pressure gauge located between the final prefilter stage and the membrane to monitor pressure rise over time is a more accurate guide to their replacement schedule. The life of these components is naturally highly dependent upon the water entering the unit. To my mind the prefilters are cheap enough to replace routinely, at least for home use, but membranes are a different matter. For my current situation using relatively large amounts of ro/di in my aquarium maintenance business, I want the maximum useful life for all components.