What Is Granular Activated Carbon? The Honest Guide
Granular activated carbon (GAC) is one of the most common water filtration media types. But what is it, and how does it work?
We’re Zooshen — we make shower filters. What we’ll tell you is the honest version.
What Is Granular Activated Carbon?
Granular activated carbon (GAC) is carbon that has been treated to create tiny pores. These pores give it an enormous surface area — a single gram of GAC can have a surface area of 500-1500 square meters.
This huge surface area is what makes it effective at adsorbing contaminants.
How Does It Work?
GAC works through adsorption — contaminants stick to the surface of the carbon as water passes through.
It’s effective at:
– Free chlorine — adsorbs chlorine and chlorination byproducts
– Organic compounds — pesticides, herbicides, VOCs
– Odors — bad tastes and smells
– Some heavy metals — partially
How It Compares
| Media | Free Chlorine | Chloramine | Hot Water | Cartridge Life |
|---|---|---|---|---|
| KDF-55 | Yes | No | Excellent | 4-6 months |
| GAC | Yes | No | Good | 2-4 months |
| Vitamin C | Yes | Yes | Good | 3-4 months |
Pros and Cons
Pros:
- Effective at reducing chlorine and odor
- Inexpensive — one of the cheapest media types
- Widely available
- Works at room temperature
Cons:
- Shorter cartridge life — 2-4 months
- Doesn’t work for chloramine
- Can grow bacteria if not replaced
- Can harbor sediment
The Honest Verdict
GAC is a solid, basic media. It works for free chlorine, but it’s:
– Shorter lasting than KDF-55
– Doesn’t work for chloramine
– More prone to bacterial growth
For the best performance, look for KDF-55 + GAC combo — KDF helps with bacteria and extends GAC life.
Zooshen Shower Filters
We’re a brand, so we’ll tell you about ours:
- KDF-55 + activated carbon (GAC) — the best combo
- NSF/ANSI 177 certified
- Tool-free install
See the Zooshen shower filter collection.
Frequently Asked Questions
What is granular activated carbon?
Carbon treated to create tiny pores, giving it enormous surface area for adsorbing contaminants.
Does GAC remove chloramine?
No. GAC removes free chlorine. For chloramine, you need vitamin C.
How long does GAC last?
2-4 months, depending on water quality and usage.
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The Bottom Line
Granular activated carbon (GAC) is a solid, basic media for free chlorine. It’s cheaper than KDF-55 but shorter lasting. For the best performance, look for KDF-55 + GAC combo.
You can read more on the activated carbon in shower filters page, or browse the Zooshen shower filter collection.
About the Author
Zooshen Water Quality Team — Zooshen is a shower filter brand focused on KDF-55 media, NSF/ANSI 177 certification, and tool-free installation.
We’re a brand, not an independent review site.
Last updated: September 25, 2026.