The pre-filters (sediment and carbon) do not normally remove TDS (Total Dissolved Solid[s]). They are there for the removal of particulate and chemical matter such as rust, sand, chlorine, etc. This applies to all micron sizes, even if you use/are using a 0.5 micron pre-filter. TDS is removed by one of the following: Reverse Osmosis (RO), De-ionization (DI) or Distillation. Normally, the RO and DI are combined for a complete removal system. The RO process cannot remove all of the TDS on its own. The DI process and distillation can. The DI lifespan depends on what the TDS feeding it is like. This is why the RO process is recommended before a DI filter. The DI is done by mixing anion and cation resins for ion removal. Distillation is the process of removing water vapors from TDS. The RO and/or RODI process is more efficient, economical and easier to use than any other process of water filtration.