sediment filters every 6 months
carbon filters every year
DI is color changing resin, so that gets changed when the color changes
RO membrane about every 2 yrs or so...TDS meter determines exactly when it needs to be changed
Mine is pretty sparatic. I change the filters once TDS goes above 7-9 and resin when I start getting PO4 in the water. DI membrane once a year.
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Some people are like slinkies...they serve no real purpose yet can still bring a smile to your face when you push them down the stairs!:p
Have a great day! Brian