When to replace RO/DI filters and membranes.

[zantho]

How do you personally decide when it's time to replace the filters and membranes? By the total gallons passed through it? The age? Or when your TDS meter reads > X PPM?
And what's the highest PPM you would allow to come out of your unit for a FOWLR tank? Also, the highest you'd allow for a reef?

 

[bang guy]

TDS meter will tell you when to replace to RO membrane & the DI rosins.
Replace the carbon once a year and the sediment when it's noticeable dirty.
For DI water anything worse than 1ppm is unacceptable. For RO I'd say 20ppm depending on the water source.

 

[zantho]

I just picked up a used Kent RO 200 HI-F. I saw in another thread that people found filters at Sears (https://www.saltwaterfish.com/vb/showthread.php?t=240323) are the filters a standard size on most of these? Or does it depend on the unit?