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Activated Carbon Filters

Activated Carbon Filters for pre-treatment in Reverse Osmosis Water Filters


Activated carbon filters are an intrinsic part in any residential or commercial reverse osmosis water filter.   Without activated carbon filters,  RO  membranes will rapidly deteriorate due to the presence of chlorine or chloramines in water supplies treated with secondary disinfection chemicals. 

To prevent oxidation on thin-film RO membranes, the feed water must be dechlorinated. Most membranes will have some chlorine tolerance before there is an observable decrease in salt rejection. Chlorine on the membrane can be discovered by an initial loss of membrane flux followed by an increase in membrane flux and salt passage.

For Dow FilmtecTM RO membranes, degradation can occur after about 500  hours of exposure to 1 mg/L ( ppm) of free chlorine. Unfortunately, chlorine damage is irreversible with any RO membrane, so proper steps must be taken to prevent it.   The activated carbon filter in a reverse osmosis water  system needs to be protected by a sediment filter of 5 micron or less.  Without a sediment filter, there will be an accelerated rate of flux decay  and increased pressure drop impacting on membrane performance,   Activated carbon filters in reverse osmosis water filters are typically installed as two pre-filters and one post filter used for final polishing of the permeate.  The increasing use of chloramines requires longer retention time and hence multiple stages to ensure adequate contact time removes any traces of chloramine. The selection of the activated carbon filters needs to consider the flow rate and water contaminants present in the water.

Benefits of Activated Carbon Filters:

  • Removes any objectionable taste and odour from the water supply.
  • Protects the RO membrane from chlorine damage.
  • Removes organics and to a lesser degree  tannins from the water supply.
  • Removes chlorine and to a lesser degree chloramines from water. 
  • The very high specific surface area means that the activated carbon has a very high capacity to absorb impurities and contaminants in your water.

Types of Activated Carbon Filters:

  1. Granular Activated Carbon( GAC)  Filters:  Typically sourced from coconut or coal, granular is a popular choice in water treatment.
  2. Carbon Block Filters:Solid carbon blocks are one of the most effective and widely used technologies in the Point Of Use (POU) drinking water treatment industry. Carbon block is mainly comprised of activated carbon granules and a binding agent that allows the carbon granules to maintain a static position relative to each other. 

The activated carbon filters can be supplied in different standard cartridge sizes   as listed below:

10″x2.5″ Activated Carbon cartridge

10″x4.5″ Activated Carbon cartridge

20″ X2.5″Activated Carbon cartridge

20″X4.5″ Activated Carbon cartridge (Jumbo cartridge)

In-line Activated Carbon cartridge  10″ x2”  typically used  as polishing filters 

In-line granular activated carbon(GAC) filters can be  fitted to any residential RO system

In-line granular activated carbon(GAC) filters can be fitted to any residential RO system

The frequency of replacement depends on water usage and water quality and the following should be used as a guideline:

Activated  Carbon GAC and Carbon Block Filters  used as pre-filters: 

Residential POU and whole house filtration: Every 6 months 

Commercial Applications:  Every 3 months

Polishing filters : In-line GAC Filters:

Residential POU and whole house filtration: Every 12 months 

Commercial Applications:  Every 6 months


Pacific Water Technology stocks the entire range of activated carbon filters  suitable for all RO systems. All our activated carbon filters are independently verified by the NSF.  Our warehouse is located in  Brisbane and we ship to all states of Australia. As an importer and manufacturer our products are competitively priced and  we only supply high performance filtration media.