A clear housing for the sediment filter is a must have,
IMO. The same for the
DI if you have color changing resin. The charcoal filters should be replaced annually.
I replace the sediment filter ~every 2 months, the charcoal filters annually, and I start checking
tds when I see that the
DI resin has changed color all the way to the top of the cannister. I have two refillable cartridges for the
DI resin. I let the old one dry out completely as I find it's much easier to empty it.
A pressure guage is also a must
IMO, though you can always add one in line if your unit didn't come with one.