Franklin FWGC20B 20-Inch Big Blue GAC Filter Cartridge

Reduce Chlorine, Unpleasant Tastes and Odours with a 4.5 x 20-Inch GAC Cartridge Tested for 25,000 Gallons at 4 GPM

The Franklin FWGC20B is a 20-inch Big Blue granular activated carbon (GAC) filter cartridge for compatible 4.5 x 20-inch housings. It helps reduce chlorine, tannin, colour, objectionable tastes and odours, trihalomethanes (THMs), turbidity, herbicides, pesticides, insecticides and volatile organic compounds (VOCs).

Franklin reports an estimated chlorine, taste and odour capacity of 25,000 gallons (95,000 litres) at 4 GPM. This capacity is based on the manufacturer's internal testing with 2 ppm free available chlorine at continuous flow and greater than 75% reduction. Actual performance and service life vary with water quality, flow and operating conditions.

Key Features and Benefits of Franklin FWGC20B 20-Inch Big Blue GAC Filter Cartridge

• Granular activated carbon media: Helps reduce chlorine and objectionable tastes and odours, so treated water can taste and smell better.
• Full-length carbon bed: Water travels through the length of the media before leaving the cartridge, so the system uses the intended carbon path.
• Internal expansion pad: Helps limit channeling and bypass, so more of the carbon bed can contribute to treatment.
• 25,000-gallon estimated capacity at 4 GPM: Gives you a planning benchmark under Franklin's stated chlorine test conditions.
• Nominal 4.5 x 20-inch Big Blue format: Fits compatible 20-inch Big Blue-style housings, so you can replace the cartridge without changing a correctly matched housing.
• NSF/ANSI 42 materials certification: Confirms the cartridge materials meet the stated NSF/ANSI 42 material requirements. This does not mean every listed contaminant-reduction claim is NSF certified.

What Does the FWGC20B Help Reduce?

Franklin lists the FWGC Series for significant reduction of:

• Chlorine
• Chlorine by-products, including THMs
• Objectionable tastes and odours
• Turbidity or cloudy water
• Colour and tannin
• Herbicides, pesticides and insecticides
• Volatile organic compounds (VOCs)

This cartridge does not disinfect water or make microbiologically unsafe water safe to drink. Franklin recommends multiple disinfection barriers when treating raw water with known or suspected pathogens.

Does the FWGC20B Fit Your Housing?

The FWGC20B has a nominal 4.5-inch diameter and 20-inch length. Its listed dimensions are 110 mm (4.35 inches) OD, 508 mm (20 inches) long and 28 mm (1.1 inches) ID. It fits most compatible 20-inch Big Blue-style housings, including the appropriate model from the Franklin FWHL Big Blue filter housing series.

Before ordering, confirm the housing length, cartridge diameter, end configuration and available service clearance. The product options on this page are one FWGC20B cartridge or a case of six filters.

Technical Specifications

Capacity note: The 25,000-gallon estimate is not a fixed replacement interval. Franklin's internal test used 2 ppm free available chlorine at continuous 4 GPM with greater than 75% reduction. Actual results can vary widely.

Common Applications

• Potable and process water treatment
• Point-of-use and properly sized point-of-entry systems
• Residential and commercial water purification systems
• Food and beverage water treatment
• Reverse osmosis pre-filtration or post-filtration

The FWGC20B may be used in a whole-house system only when its published 4 GPM flow and 10 psi initial pressure drop meet the home's peak water demand. A larger housing, parallel treatment train or different cartridge may be required for higher flow.

Before Ordering

• Confirm that your housing accepts one nominal 4.5 x 20-inch Big Blue-style cartridge.
• Check whether 4 GPM and a 10 psi initial pressure drop fit your system.
• Keep operating pressure at or below 150 psi.
• Keep water temperature between 4°C and 50°C (40°F and 120°F).
• Use a separate sediment prefilter when the water contains sand, rust or other suspended solids. Browse the Franklin 20-inch Big Blue sediment filter cartridges.
• Select treatment equipment from a current water test and the contaminants you need to reduce.

The FWGC20B is a carbon cartridge, not a rated sediment filter. Franklin does not publish a micron rating for this model. If you need a different carbon-media format, compare the Franklin Big Blue carbon block cartridges.

Installation and Flushing

1. Shut off the water supply and release pressure from the housing.
2. Remove the used cartridge and clean the housing according to its instructions.
3. Inspect the gasket or O-ring and replace it if damaged.
4. Install the FWGC20B in the correct flow direction when a direction is marked.
5. Reassemble the housing, restore water slowly and check for leaks.
6. Flush the cartridge until any carbon fines clear before using the water.

Carbon cartridges may release a small amount of fine black powder during initial flushing. Franklin also advises flushing the tap for at least 20 seconds before using water for drinking or cooking, especially when the tap has not been used daily.

FWGC10B vs. FWGC20B

Choose the model that fits your housing and required flow. The larger capacity shown for the FWGC20B comes from a different test flow, so it should not be treated as a guaranteed service-life comparison.

Buy the Franklin FWGC20B 20-Inch Big Blue GAC Filter Cartridge from Cleanflow

Choose one cartridge or a case of six. Confirm your housing size, required flow and water-treatment goal before ordering. For more options, browse Big Blue water filters and cartridges, read the Big Blue water filter buyer's guide, or view more Franklin Water Treatment products.

Frequently Asked Questions

What size housing fits the FWGC20B?

Use a compatible housing made for one nominal 4.5 x 20-inch Big Blue-style cartridge. Confirm the housing length, internal dimensions and end configuration before ordering.

What contaminants does the FWGC20B help reduce?

Franklin lists chlorine, THMs, objectionable tastes and odours, turbidity, colour, tannin, herbicides, pesticides, insecticides and VOCs. Actual reduction depends on the contaminant, concentration, flow and water conditions.

How long does the FWGC20B last?

Franklin estimates 25,000 gallons for chlorine, taste and odour reduction at 4 GPM under its stated test conditions. This is not a guaranteed replacement interval. Replace the cartridge when treatment declines or pressure drop reaches the system's service limit.

Can the FWGC20B be used for whole-house filtration?

Yes, if its published 4 GPM flow and 10 psi initial pressure drop meet the system's peak demand. Many homes require more flow, so confirm the complete system design before ordering.

Is the FWGC20B a sediment filter?

No. It is a granular activated carbon cartridge, and Franklin does not publish a micron rating for it. Install a separate sediment cartridge upstream when suspended solids are present.

Can it be installed before or after reverse osmosis?

Yes. Franklin lists the FWGC Series for RO pre-filtration and post-filtration in residential and commercial systems. Confirm the required flow, pressure and treatment goal for the installation.

What does the NSF/ANSI 42 certification cover?

Franklin states that the cartridge is tested and certified to NSF/ANSI 42 for material requirements only. Do not interpret this as NSF certification for every contaminant-reduction claim listed on the page.