How often do you have to replace the filters on RO/DI units?

[bmkj02]

I have a 125g tank. Thinking of purchasing a ro/di unit to avoid going so much to the LFS for water. How often do these filters have to be replaced and whats a good not so expensive brand. I have seen unit for $160 to like $400. I know you get what you pay for but sometimes its just name brands. Thanks

 

[florida joe]

I answered in the same thread you started in new hobbyist

 

[jackri]

Depends on how much water you run through them and the quality of water going through. I have really bad city water (REALLY bad) and I'm changing them twice as often as recommended... the filters are absoutely nasty when I do.