[michael robinson]

hi guys just wondering about ro machines the pre filters on the bottom the three tubes how often should they be changed?? Next questions the two smaller ones on top is that the membrane? do these have to be changed? i can't find info about them anywhere. Suggestions on those questions would be appriciated.

[mark dew]

Yes they all need to be changed sometime. But if they are flushed regularly they last a long time.
How to tell is that the tds rises after going through the RO unit. The 1st thing will be the filters. They are very cheap.
Once these have been replaced and are installed properly, if the tds is still higher than normal then change the membranes.
I'm on the same membranes for 3 1/2 years now. I have changed the filters once.