I want to take a moment to discuss a very basic and important reverse osmosis topic; Pre-filters.

>Sediment filters are designed to remove dirt and large particles from the water. They tend to look dirtier than the other filters; even when first used. This is normal and nothing to worry about.

>Carbon filters are designed to remove chemicals mixed with the water as well as removing sediment.

The optimal situation is to progressively remove the dirt/sediment. This helps distribute the work load and prevents excessive pressure drops. We do this so the first filter protects the next and so on. This helps improve the filter life and improves the overall performance of the system.

Our normal pre-filter array is as follows:
Stage 1 - A ten micron sediment filter
Stage 2 - A five micron coconut carbon block
Stage 3 - A one micron coconut carbon filter

Smaller micron rated filters can remove more, but will clog faster. This is why we don't normally use them.

The manufacturer of the FilmTec reverse osmosis membrane requires the removal of oxidants/chlorine and of particles/sediment larger than five (5) micron to comply with its three year warranty.
(www.filmtec.com)

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.

As mentioned before, the sediment and carbon filters are only there to remove particulate and chemical matter before it reaches and fouls the RO membrane. There are a few different kinds of carbon - Carbon block, GAC, catalytic and PAC. We normally use two carbon block filters for their superior chlorine removal and its ability to remove some chloramine. The catalytic carbon is used mainly for chloramine removal.

The RO membrane is there for removal of bacteria, viruses, pathogens, endotoxins, metals, salts and other TDS. Keep in mind that this process still leaves some TDS, but it's within safe levels.

The DI is normally used as a post filter for the membrane. It removes the remaining TDS by the ion exchange process using anion and cation resin beds. Its main function is to remove the rest of the salt and metal ions from the water.

For drinking water units, a "Taste and Odor" filter is installed after the RO membrane. This does not remove any TDS, but it cleans up any taste or odor that may be left after the RO process.

CAUTION!! - Before installing new filters, make sure that the water supply is turned off and the pressure has been released from the unit. This can be done by opening a pure water output line.

Vertical Filters:
(Mainly the pre-filters unless on a smaller unit):

Unscrew the filter housings. Remove old filters from the unit. Install the new filters, making sure they're in the right order:
Stage 1 - 10 micron sediment
Stage 2 - 5 micron carbon block (normally)
Stage 3 - 1 micron carbon block.
Stage 5 - After the RO membrane and only if you have a vertical DI.

Make sure to hand tighten the housings back. Too much tightening can lead to the housing cracking apart.

In-line Filters:

The in-line filters normally have push-in fittings. Simply remove the tubing and/or fittings from the filter. Install the new filters making sure of the direction of flow.

In-line filters can be used as pre-filters on smaller units, though they're mainly used as post-filters. The standard in-line filter is 5 microns. If you have a unit with the in-line filters as your pre-filters, the setup is as follows:
Stage 1 - In-line carbon
Stage 2 - In-line sediment

The reason for this is the in-line carbon tends to release grains of carbon which can clog the RO membrane. The sediment follows after it to prevent this from happening.

RO Membrane:

Remove the old membrane by using either a pair of pliers or a screwdriver to put through the holes i the plastic center of the membrane. Make sure that the new membrane has its O-rings well lubricated. Install the new membrane with the O-rings in the housing first.

These are basic instructions for standard filters and may not apply to all units.