20 Inch Big Blue GAC Cartridge
Chlorine and smell at whole-house flow, with more contact time than a block.
Granular coconut-shell activated carbon in a 20 by 4.5 inch cartridge. Where a carbon block filters finer, loose granules give the water more time in contact with carbon, which is what heavily chlorinated or smelly supplies need. Fits the second housing of the AquaGuard or any Big Blue unit, or a single housing as a dedicated carbon stage.
Block or GAC
The carbon block is the default: it filters to 5 micron as well as adsorbing chlorine. GAC has no micron rating of its own but holds more carbon and gives the water longer contact, so it lasts longer on high-chlorine water and does better against taste and smell. Run it after a 5 micron sediment stage, never first.
When to change it
Six to twelve months, when the chlorine smell returns at the taps. Flush ten minutes on fitting; the grey water is fines.
