Replacement Filters · Carbon Filters
Select your filter size, carbon type, and connection — we’ll show you exactly what fits.
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Isopure Water · Filter Cartridges & Replacement Filters
Carbon Filters — Better Water from Every System
The workhorse of water filtration. Carbon cartridges remove chlorine, chloramines, taste, odor, VOCs, and heavy metals from RO systems, whole-house housings, under-sink setups, and Big Blue applications — all in one compact, easy-to-replace cartridge.
Carbon filters are the most commonly replaced component in any water filtration system — and also the most important for taste and chemical removal. Choosing the right filter means matching carbon type, size, and micron rating to your housing and your water chemistry. This guide walks you through every option we carry.
Carbon Types
Choosing the Right Carbon for Your Water
Activated Coconut Shell Carbon
The gold standard for residential water filtration. High-surface-area activated carbon derived from coconut shells delivers superior adsorption of chlorine and organics compared to coal-based alternatives.
- Chlorine taste & odor
- VOCs & organic compounds
- Pesticides & herbicides
- Sediment (block format)
- General taste improvement
Catalytic Activated Carbon
An enhanced carbon with a modified surface structure that enables catalytic reactions — allowing it to break down chloramines and hydrogen sulfide that standard carbon cannot address. Required when your utility uses chloramines.
- Chloramines — standard carbon cannot do this
- Hydrogen sulfide (rotten egg odor)
- Chlorine & chlorine dioxide
- VOCs & organic compounds
- Taste & odor
Granular Activated Carbon
Loose carbon granules used primarily as post-filters in RO systems to polish taste and remove residual chlorine after membrane filtration. Lower pressure drop than carbon block — used where flow rate matters more than particulate removal.
- Post-RO taste polishing
- Residual chlorine removal
- Odor improvement
KX MatriKX Pb1 — Advanced Reduction
A premium sub-micron carbon block engineered specifically for lead, cyst, chloramine, and VOC reduction. Ideal for older homes with copper/lead plumbing, or for use ahead of an RO membrane to maximize protection.
- Lead & heavy metals
- Cysts (Giardia, Cryptosporidium)
- Chloramine & chlorine
- VOCs & organics
Chlorine vs. Chloramines: Many large US cities have switched from free chlorine to chloramines as a disinfectant — a combination of chlorine and ammonia that is far more difficult to remove. Standard coconut shell carbon, while excellent for chlorine, has minimal effect on chloramines. If your utility uses chloramines, you need either catalytic carbon or KX MatriKX CTO Plus / Pb1 filters. Check your annual water quality report or call your utility to confirm.
What We Carry
Brands & Product Lines
Hydronix
Coconut Carbon Block Filters
NSF-certified coconut shell carbon block cartridges available in all standard housing sizes from 10"×2.5" slim through 20"×4.5" Big Blue. Multiple micron ratings from 0.5 to 10 micron. Available in single, two-pack, three-pack, and four-pack quantities for cost savings.
Hydronix
GAC Carbon Filters (UDF-10)
10"×2.5" granular activated carbon filter for standard RO post-filter applications. NSF-certified. Used as Stage 4 polishing filter in under-sink RO systems to improve final taste and remove residual chlorine after the membrane.
Hydronix
Sub-Micron Carbon Block (SMCB)
0.5-micron precision carbon block filters in 2.5"×10" and 4.5"×20" sizes for applications requiring tighter particulate removal alongside chlorine and chemical reduction. NSF-certified construction.
KX Technologies (MatriKX)
CTO Plus — Chloramine & VOC Reduction
The professional installer's choice for chloraminated municipal water. MatriKX CTO Plus delivers chloramine, VOC, and chlorine reduction at 1 micron. Available in all four standard housing formats for maximum versatility.
KX Technologies (MatriKX)
Pb1 — Lead, Cyst & Chloramine
Advanced 0.5-micron sub-micron block for lead, cyst, chloramine, and VOC reduction. Recommended for older homes with copper plumbing, water with elevated lead risk, or as pre-treatment for RO membranes. Available in single and multi-packs.
IPW Industries Inc.
Big Blue Carbon Block Cartridges
High-capacity 20"×4.5" CTO carbon block cartridges for Big Blue whole-house housings. Available individually or in multi-packs up to six filters for maximum value. Also available as a combination set with a matching sediment cartridge for a complete Big Blue filter change.
Micron Rating Guide
Which Micron Rating Do You Need?
| Micron Rating | What It Captures | Best Application | Flow Rate Impact |
|---|---|---|---|
| 0.5 Micron | Cysts, lead particles, fine sediment, sub-micron contaminants | Lead/cyst reduction, pre-RO, drinking water systems | Most restrictive — slower flow |
| 1 Micron ★ | Most bacteria, fine particulates, cysts | Under-sink, RO pre-filter, chloramine-rated systems — most popular choice | Moderate restriction |
| 5 Micron | Sand, silt, sediment, larger particles | Standard under-sink, RO Stage 1, general pre-filtration | Good flow rate balance |
| 10 Micron | Coarse sediment, visible particles | Whole-house pre-filter, Big Blue first-stage, high-flow applications | Minimal restriction — highest flow |
Stacking micron ratings: In multi-stage systems, run filters from coarser to finer — a 10 or 5 micron sediment filter first, then a 1 or 0.5 micron carbon block. This staged approach removes large particles first, protecting the tighter carbon block from premature clogging and significantly extending filter life.
Applications
Where Carbon Filters Fit in Your System
RO Pre-Filter (Stage 2/3)
Protects the RO membrane from chlorine damage. Standard 10"×2.5" carbon block — the most commonly replaced filter in any RO system.
RO Post-Filter (Stage 4)
GAC post-filter polishes the taste of already-purified RO water after the membrane. Keeps water fresh between the tank and the faucet.
Under-Sink & Countertop
10"×2.5" and 10"×4.5" carbon blocks used in single-stage under-sink housings and countertop systems for point-of-use drinking water improvement.
Big Blue Whole-House
20"×4.5" high-capacity carbon blocks for Big Blue housings. High flow rate, long service life — ideal as a second stage after a sediment pre-filter.
Whole-House Inline
20"×2.5" slim carbon blocks in standard housings for cost-effective whole-house chlorine reduction in lower-flow residential applications.
Specialty Applications
Hydro-Logic, GE Merlin, Culligan AquaCleer, and other OEM-compatible sizes for system-specific replacements available in our specialty filter range.
Replacement Guide
When & How to Replace Your Carbon Filter
Follow Your Schedule First
RO pre/post carbon: every 6–12 months. Big Blue whole-house: every 6–9 months. Under-sink: every 6 months. Don't wait for symptoms — carbon exhausts before you can taste it.
Watch for These Signs
Returning chlorine taste or odor, reduced flow rate through the system, or water that looks slightly discolored are all signs the filter is past its service life.
Match Size Exactly
Carbon blocks must fit the housing precisely — a 10"×2.5" filter will not seal correctly in a 10"×4.5" housing. Check your housing label or owner's manual before ordering.
Flush After Every Change
Run 3–5 gallons through a new carbon block before use. New filters shed fine carbon dust that makes the first water appear grey — this is normal and flushes out quickly.
Consider Multi-Packs
Buying 2–4 filters at once saves per-unit cost and ensures you always have a replacement on hand. Multi-packs are available across our Hydronix and KX MatriKX lines.
Not sure which filter fits your system? Our team can look up the correct replacement by brand, housing model, or system name. Call (877) 541-6603 or email support@isopurewater.com — have your current filter's part number or dimensions handy.
Coconut Shell Carbon
Higher adsorption capacity and cleaner taste profile than coal-based alternatives. The professional standard for residential drinking water.
Sub-Micron Precision
From 0.5 to 10 micron — the right block rating protects your membrane, extends system life, and meets your specific contaminant targets.
Multi-Pack Value
Stock up with 2, 3, 4, and 6-pack options across our Hydronix and IPW Big Blue lines for meaningful per-filter savings.
Universal Compatibility
Standard sizing across brands means our filters fit thousands of housings — from Pentek Big Blue to slim standard to OEM-specific formats.
