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Big Blue Filter Kits

Big Blue Filter Kits

Now offering yearly filter replacement subscriptions!

Big Blue Filter Kits for Whole-House Water Filtration

Big Blue systems use large-diameter cartridges, 4.5 inches across, in 10-inch and 20-inch lengths, and that extra bulk buys you real advantages over slimline filters: considerably more dirt-holding capacity, higher flow rates before pressure drop becomes a problem, longer intervals between changes in many households, and enough media volume to make specialty treatment viable at the whole-house level.

What Is a Big Blue Filter System?

"Big Blue" is a size format rather than a single product. It refers to the large 4.5-inch-diameter housing standard used across the industry, available in different lengths - most commonly 10-inch and 20-inch.

A complete Big Blue filter system is made up of:

  • The Big Blue filter housing - sump and top cap
  • A filter cartridge inside it, which does the actual treatment
  • A housing O-ring sealing cap to sump
  • A mounting bracket supporting the assembly
  • Inlet and outlet connections on the cap
  • A pressure-relief button on many caps, which lets you depressurise before opening
  • Additional housings where the system runs two or three stages in series

The distinction that matters for ordering: a kit contains cartridges. A complete system includes housings and hardware.

Why Use a Big Blue Whole House Filter?

This is why a big blue filter kit can be beneficial for you:

Higher Capacity Than Slimline Cartridges

A 4.5-inch-diameter cartridge holds substantially more media than a 2.5-inch slimline of the same length, with far more surface area facing the water. The practical effect is that it takes longer to load up with sediment, and there is more carbon or specialty media available to do chemical work before exhaustion.

Flexible Staged Filtration

Big Blue filtration is built around stages. A two-stage or three-stage system lets you combine treatments that no single cartridge could deliver - typically a sediment stage protecting a carbon or specialty stage, sometimes with a third cartridge polishing or targeting a specific contaminant. Our kits are assembled around exactly these combinations.

Point-of-Entry Treatment

Installed on the main line where water enters the building, a Big Blue whole house filter treats everything downstream. Showers, taps, laundry, the water heater, and any drinking-water system further along all get filtered water.

Easy Cartridge Replacement

Housings stay put. When a cartridge is spent, you shut off the water, relieve pressure, unscrew the sump, swap the cartridge, and reassemble. The housing is a long-term fixture; the cartridge is the consumable.

Shop Big Blue Filter Kits by Treatment Type

These are some of the top big blue filter kits you can choose from:

Sediment and Carbon Block Kits

The most common configuration in the range, and the right starting point for most municipal supplies. The sediment cartridge takes out sand, rust, silt, and particulates; the carbon block handles chlorine, taste, odor, and a range of chemicals.

Available as the 20-inch Sediment and Carbon Block 2 Stage Filter Kit and the 10-inch (10"×4.5") Sediment and Carbon Block 2 Stage Filter Kit. The 20-inch kit pairs a high-flow 5–10 micron sediment cartridge with a 5–10 micron carbon block, both approximately 19.75" × 4.5".

GAC and KDF Kits

Granular activated carbon combined with KDF 55 media broadens the treatment range beyond what carbon does alone, covering taste, odor, chlorine, and certain chemical and metal applications. These are not universal contaminant removers; what they achieve depends on your water chemistry, concentration, and contact time.

Catalytic Carbon and KDF-85 Kits

Catalytic carbon is the upgrade path when ordinary carbon is not keeping up - chloramine, higher chlorine loads, and hydrogen sulfide. KDF-85 differs from KDF 55 in that it addresses iron and hydrogen sulfide, which KDF 55 does not.

Activated Alumina Kits

Activated alumina is used in targeted applications for fluoride, arsenic, and lead reduction. Performance is sensitive to pH, competing ions, flow rate, and contact time, so this media genuinely requires a water test first - and confirmation that the specific cartridge suits your water chemistry.

Bone Char Carbon Kits

Bone char is used for fluoride, arsenic, radioactive particles, and selected toxic metals. As with activated alumina, results depend on your specific water, and testing before purchase is not optional if you are treating a health-related contaminant.

Radial-Flow Carbon Kits

Radial flow carbon delivers carbon treatment in a format designed to reduce the loose-carbon migration that conventional GAC cartridges can produce - the black grit that occasionally shows up in a glass after a filter change. Available in several two- and three-stage combinations.

Specialty and Multi-Stage Kits

Beyond the standard media, the category includes kits targeting specific contaminants:

  • Nitrate: 20-Inch 2 Stage Kit - Sediment & Nitrate Filtration; and a 3 Stage Kit with Sediment, Carbon Block, and Nitrate Filters
  • Lead: 20-Inch 2 Stage Kit with Sediment & Matrikx Pb1 Filters; and a 3 Stage Kit with Sediment, Carbon Block, and Matrikx Pb1
  • Arsenic: 20-Inch 2 Stage Kit with Sediment & AdEdge Bayoxide® E33 Filter Cartridges; and a 2 Stage Kit with Sediment Filter & LayneRT Filters
  • pH correction: 2 Stage Neutralizing Filter Kit for Sediment & pH Balance; 2 Stage pH Neutralizer Calcite & GAC with KDF 55; 3 Stage Sediment, pH, Radial Flow Carbon; 3 Stage Sediment, pH and Bone Char; 3 Stage Sediment, pH, and KDF 55; and 3 Stage Sediment, pH Filter and Catalytic Carbon with KDF 85
  • Deionization: 20-inch High Flow 2 Stage Filter Kit with Dual DI Filters

How to Choose the Right Big Blue Filter Kit

Follow these steps to choose the perfect big blue filter kit:

Match the Kit to Your Existing Housing

Before anything else, confirm the physical fit:

  • Length: 10-inch or 20-inch
  • Diameter: 4.5 inches (the Big Blue standard)
  • Number of stages: how many housings you have in series
  • Cartridge dimensions: 20-inch Big Blue cartridges run approximately 19¾" × 4½"
  • End configuration and gasket compatibility - most Big Blue cartridges are open-ended, but check

Match the Media to the Water Problem

Water problem Common Big Blue cartridge type
Sand, rust, visible sediment Polypropylene sediment filter
Fine particulate Lower-micron sediment filter (1-micron)
Chlorine, taste, odor Carbon block or GAC
Chloramine, difficult chemical loads Catalytic carbon
Hydrogen sulfide, iron Catalytic carbon with KDF-85
Fluoride, some arsenic applications Activated alumina or bone char
Lead Matrikx Pb1
Nitrate Nitrate-specific cartridge
Low pH, blue-green staining Calcite/corosex neutralizing blend
Multi-contaminant treatment Two- or three-stage matched kit

First, test your water with water test kits and TDS meters and check the individual product specifications before committing to a specialty media.

Two Stages or Three?

Two-stage systems are simpler, take up less wall space, and cost less to maintain. For chlorinated municipal water, sediment plus carbon block handles most of what people actually notice.

Three-stage systems give you room for a third treatment - a specialty cartridge, or a polishing stage. The trade-offs are real: more housings mean a larger installation, more pressure drop, and three cartridges to replace instead of two.

Flow Rate and Pressure Drop

The more bathrooms and fixtures, the more headroom you need. Every cartridge adds some pressure drop when clean, and considerably more as it loads with sediment. Check the flow ratings on the specific cartridges you are considering rather than assuming Big Blue diameter alone solves it.

Kits vs. Complete Systems: What You Are Buying

Item What it is
Filter kit Matched replacement cartridges for an existing system
Filter housing The canister that holds a cartridge - cartridge usually sold separately
Bracket Steel mount supporting one or more housings
Complete system Housings, bracket, cartridges, fittings, and often a wrench

If you are replacing spent media in a system you already own, you want a kit. If you are building a system from scratch, start with whole house cartridge systems or 20" Big Blue systems.

Frequently Asked Questions

That depends entirely on the cartridge inside it. Sediment cartridges trap sand, rust, silt, and particulates. Carbon block and GAC address chlorine, taste, and odor. Catalytic carbon handles chloramine and hydrogen sulfide. Specialty cartridges target fluoride, arsenic, lead, or nitrate. The housing is just a housing - the cartridge does the work.

A matched set of replacement cartridges for your system's stage count and housing size. A two-stage kit contains two cartridges; a three-stage kit contains three. Kits do not include housings, brackets, or wrenches.

Match your existing housings. Measure cartridge length - 10-inch or 20-inch - and count your stages. Big Blue cartridges are 4.5 inches in diameter; 20-inch cartridges measure approximately 19¾" × 4½".

AFW's guidance is at least once a year, with six months being average for most homes. Heavier sediment loads, well water, and high household usage shorten that interval. Reduced pressure or the return of chlorine taste means change them regardless of how long it has been.

Neither is universally better. Carbon block is solid carbon and is used where chlorine, chemical, taste, and odor reduction is wanted, and it also provides some particulate filtration. GAC is granular and typically allows higher flow with less pressure drop. Radial flow carbon is a third option designed to reduce carbon migration into the water.