20-inch Big Blue Filters

Why Choose a 20-Inch Big Blue Replacement Filter?

• Media volume: A 20-inch cartridge holds roughly twice the media of a 10-inch cartridge of the same diameter. For reference, the empty 20-inch shell holds just under 0.2 cubic feet - that is the space available for carbon, calcite, or specialty media to do their work.
• Capacity and service life: More media means more contaminant capacity before exhaustion and more dirt-holding capacity before pressure drop becomes noticeable. In many households, that translates directly into longer intervals between changes.
• Flow: The 4.5-inch diameter gives more surface area facing the water, which is what keeps pressure drop manageable at whole-house flow rates.
• Standard fit: These cartridges fit standard 20-inch Big Blue housings across most brands, so you are not locked into a manufacturer.

The length and diameter must match the housing. A 20-inch cartridge will not seat in a 10-inch housing, and a slimline cartridge will rattle around uselessly in a 4.5-inch sump. Measure before you order.

Shop 20-Inch Big Blue Filters by Media Type

Check out the best way to shop for a 20-inch Big Blue filter:

Sediment Cartridges

Available in 10-micron, 5-micron, and 1-micron ratings, plus a pleated sediment option. These trap dirt, sand, rust, and particulates.

Choosing a micron rating is a genuine trade-off. A 1-micron cartridge catches finer particulate but clogs faster and drops more pressure. A 5- or 10-micron cartridge passes finer material but lasts considerably longer and maintains flow.

Carbon Block Filters

The Big Blue 20-inch Carbon Filter, 5-micron is solid carbon block, used where chlorine, chemical, taste, and odor reduction is the goal. Being solid rather than granular, it also does some particulate filtration on the way through.

GAC and Radial-Flow Carbon

The Big Blue 20-inch GAC Filter and GAC/KDF 55 and GAC/5# KDF 55 options use granular activated carbon, which generally allows higher flow with less pressure drop than a solid block.

The Big Blue 20-inch Radial Flow Carbon (SKU RF-4520-20) takes a different construction approach, designed to reduce the carbon fines migration that granular cartridges sometimes produce - the fine black grit that can show up at a tap after a filter change.

Catalytic Carbon and KDF Filters

Three options here: Catalytic Carbon, Catalytic Carbon/KDF 85, and Catalytic Carbon/5# KDF 85.

The distinction that matters: catalytic carbon media addresses a wide range of tastes, odors, and chemicals, including chlorine, herbicides, pesticides, and hydrogen sulfide. KDF 85 handles iron and hydrogen sulfide, which KDF 55 does not. If sulfur smell or iron is your problem, that is the difference to pay attention to.

Bone Char and Activated Alumina

The Big Blue 20-inch Activated Alumina Filter (SKU AA-4520) is listed for fluoride, arsenic, and lead. The Big Blue 20-inch Bone Char Carbon Filter (SKU BC-4520) is listed for fluoride, arsenic, radioactive particles, and toxic metals.

Both are also available in arsenic-specific alternatives: the AdEdge Bayoxide® E33 Filter for Arsenic, and Matrikx Pb1 Lead Filter for lead specifically.

pH and Phosphate Filters

The Big Blue 20-inch pH Filter contains a blend of 40% calcite, 40% GAC, and 20% corosex. The calcite and corosex dissolve slowly to neutralise acidic water - the cause of blue-green staining on fixtures and corrosion in copper pipe - while the GAC maintains flow and handles taste and odor.

The Big Blue 20-inch Phosphate Filter (SKU PO-4520) is for scale prevention. Worth being clear about the distinction: a phosphate cartridge inhibits scale from forming; it does not remove hardness. Your water is still hard. If you want hardness reduced, you need an ion-exchange water softener, not a cartridge.

Nitrate and DI Filters

The Big Blue 20-inch Nitrate Filter (Aries AF-20-3610-BB) targets nitrate. The 20-inch Big Blue DI Filter provides deionization for applications requiring it.

Empty Cartridge Shells

The Big Blue 20-inch Empty Cartridge Shell lets you build a custom filter with media of your choosing, or refill and reuse the shell once media is exhausted. It includes the shell, seal, an extra-thick foam sediment pad, and a shrink-wrap plastic sleeve for sealing the filter for storage. It holds just under 0.2 cubic feet and fits all standard 20-inch Big Blue housings.

How to Choose the Right 20-Inch Big Blue Filter

• Confirm your housing dimensions: 20-inch length, 4.5-inch diameter
• Identify your current cartridge type; check the old one before you throw it out
• Match the micron rating to your sediment load, coarser if the load is heavy
• Match the media to the contaminant, based on a water test
• Check flow rate and pressure-drop implications for your household's peak demand
• Confirm the end configuration fits your housing
• Note flushing requirements; carbon and specialty cartridges usually need flushing before use