My concerns would be that there is no pressure gauge, so you don't know how your membrane is doing. There is no TDS meter, so you do no know if your DI is going and you can't see any of your filter cartridges so you have to take it apart to see if your sediment is dirty or your DI is exhausted.
I am certainly no expert on RO
units, but I thought that *most* RO
membranes are good for around 2-5 years or so. So lets say we shoot for replacing it in 3 years.
Also I think that regular maintenance of the sediment filter calls for replacing it every 6 months and the GAC
filters should be replaced once every year.
You are correct, though, that without a TDS
meter, one cannot measure dissolved solids in the water. So we would be guessing about when to replace the DI
resin. But I think a safe guess would be around the 2 year area. Perhaps the same time the membrane is replaced...