← Technology WikiCTO Carbon Block Filter
A CTO (chlorine, taste, odor) carbon block is a compressed activated-carbon filter that removes chlorine, bad taste/odor, and organics — and protects the RO membrane from chlorine damage.
How it works
- Made by compressing powdered activated carbon with a binder into a solid block.
- Adsorption (not just straining): contaminants stick to the carbon's huge internal surface area.
- Critical job in RO systems: removing free chlorine, which destroys TFC RO membranes on contact.
- Nominal ratings typically 5–10 microns; the block structure gives longer contact time than granular carbon.
Key specifications
| Function | Chlorine / taste / odor removal |
| Media | Compressed activated carbon |
| Typical rating | 5–10 micron nominal |
| Typical lifespan | 6–12 months |
What buyers and QC should check
- This is the membrane's bodyguard — never skip it in an RO chain, and never extend its life past spec in chlorinated water.
- Ask for iodine number / chlorine capacity data, not just dimensions — cheap blocks exhaust fast.
- For QC: verify no carbon fines (black water on first flush beyond normal).
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
CTO vs UDF — what's the difference?
CTO is a compressed block (longer contact time, finer filtration); UDF is loose granular carbon (higher flow, shorter contact). RO systems typically use both: UDF first, CTO second.
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