Pentek RFC20-BB Radial Flow Carbon Filter - 20" Jumbo 4.5", High Flow GAC NZ

The highest capacity Pentek radial flow GAC cartridge — for Jumbo (Big Blue) 20" x 4.5" housings, with exceptional chlorine reduction capacity and very low pressure drop. The Pentek RFC20-BB is a radial flow GAC cartridge designed for point-of-entry and high-flow whole-house applications. The unique radial flow design passes water through a bed of granular activated carbon from the outside in, reducing chlorine, taste, and odour at high flow rates while keeping pressure drop low. The 70-micron porous polyethylene outer shell contains the carbon bed and significantly reduces the release of carbon fines into the filtered water — a common issue with standard GAC cartridges. The 20" length doubles the carbon bed volume compared to the RFC-BB 10", delivering a manufacturer-stated chlorine reduction capacity of over 378,541 litres at 15.2 L/min — suited to large homes, farms, and high-demand whole-house installations. NSF/ANSI Standard 42 certified for material requirements only. Chlorine reduction figures are manufacturer-stated. Key specs at a glance Filter media: granular activated carbon (GAC) Size: 4.5" x 20" (114mm x 508mm) — Jumbo / Big Blue 20" Chlorine reduction capacity: >378,541L @ 15.2 L/min (manufacturer-stated) Initial pressure drop: 0.06 bar (0.90 psi) @ 15.1 L/min Temperature range: 4.4–51.7°C NSF/ANSI 42 certified — material requirements only Suits point-of-entry and high-flow whole-house installations How it works Standard GAC cartridges can release carbon fines — fine carbon particles — into filtered water, particularly when flow rate varies. The RFC20-BB uses a radial flow design: water enters through the 70-micron porous polyethylene outer shell and flows radially inward through the carbon bed to the spun polypropylene core. This construction contains the carbon bed and substantially reduces fines in the filtered water while keeping pressure drop low. The 20" length provides double the carbon bed volume of the 10" RFC-BB, which means a longer service life between replacements and higher capacity at any given flow rate — making it the better choice for large homes and high-demand installations where changing cartridges frequently is inconvenient. Full specifications Specification Detail Filter media Granular activated carbon (GAC) Outer shell 70-micron porous polyethylene Core Spun polypropylene Endcaps Polypropylene Gaskets Buna-N Size 4.50" x 20" (114mm x 508mm) Housing compatibility Jumbo (Big Blue) 20" housings Initial pressure drop 0.06 bar (0.90 psi) @ 15.1 L/min Chlorine reduction capacity >378,541L @ 15.2 L/min (manufacturer-stated) Temperature range 4.4–51.7°C NSF certification NSF/ANSI 42 — material requirements only Part number RFC20-BB (155247-43) What's in the box 1 x Pentek RFC20-BB radial flow carbon cartridge Frequently asked questions What is a radial flow carbon cartridge and how is it different from a carbon block? A radial flow cartridge uses loose granular activated carbon packed between an outer shell and an inner core. Water flows radially inward through the carbon bed. Unlike a carbon block, the GAC design offers very low pressure drop and high flow capacity — better suited to main water line and whole-house applications where flow rate is more important than fine particulate filtration. Why does the radial flow design reduce carbon fines? The RFC20-BB's 70-micron porous polyethylene outer shell contains the carbon bed and acts as a barrier that substantially reduces the release of carbon fines into the filtered water — a common issue with standard loose GAC cartridges. What does NSF/ANSI 42 certification mean for this cartridge? The NSF/ANSI 42 certification on the RFC20-BB covers material requirements only — it confirms the materials in contact with drinking water are safe. It does not certify the chlorine reduction performance claim. That figure is manufacturer-stated based on internal testing. Why choose the 20" over the 10" RFC-BB? Double the length means double the carbon bed volume, which delivers a significantly longer service life between replacements and higher capacity at any given flow rate. If you want to minimise how often you change cartridges on a high-demand system, the 20" is the better investment. Will it fit my existing housing? Yes, if your housing is a standard Jumbo (Big Blue) 20" x 4.5" size. If you're unsure, check your housing's internal diameter and length before ordering — 10" and 20" cartridges are not interchangeable. How often should I replace it? Replacement depends on water quality and usage. The manufacturer states a chlorine reduction capacity of over 378,541 litres at 15.2 L/min. Replace when chlorine taste or odour returns, or when flow drops noticeably. Can I use this on tank or bore water? Yes, as a chlorine, taste, and odour reduction stage on disinfected supplies. This cartridge does not filter fine sediment — pair with a sediment pre-filter on tank or bore supplies.