← Technology WikiUDF / GAC Granular Carbon Filter
UDF (up-flow) / GAC (granular activated carbon) filters use loose carbon granules for high-flow chlorine and odor removal — the workhorse pre-treatment stage before CTO blocks.
How it works
- Loose granules give high flow rates with low pressure drop.
- Up-flow design (water enters bottom) fluidizes the bed slightly for even contact.
- Removes chlorine, odors, and some organics; less fine filtration than CTO blocks.
- Standard 10-inch cartridge; granule mesh size (e.g., 12x40) determines performance.
Key specifications
| Media | Granular activated carbon |
| Mesh size (typical) | 12x40 |
| Flow advantage | High flow, low pressure drop |
| Typical lifespan | 6–12 months |
What buyers and QC should check
- Check carbon source (coconut shell vs coal) — coconut-shell GAC is the drinking-water standard.
- For QC: rinse test for carbon dust; excessive fines indicate poor granule quality.
Free one-page QC checklist (PDF)
The buyer checks from this entry, condensed for the factory floor or the inspection. No signup needed.
Download free PDF checklistCommon questions
Coconut shell vs coal-based carbon?
Coconut-shell carbon has more micropores (better for taste/odor/organics) and is the standard for drinking water. Coal-based is cheaper and common in industrial use.
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