Why Activated Charcoal Water Filters Are So Effective

Activated charcoal (activated carbon) is the most widely used filtration media in home water filters — and for good reason. Here’s a clear explanation of how it works and what it removes.

Browse our 8-stage KDF filters (which include activated carbon stages) or our replacement cartridge range.

What Is Activated Charcoal?

Activated charcoal is carbon that has been treated with oxygen at high temperature to create millions of microscopic pores. This process dramatically increases the surface area — a single gram of activated carbon can have a surface area of 300–2,000 square metres. That enormous surface area is what makes it so effective at trapping contaminants.

The key mechanism is adsorption (not absorption). Contaminants bond chemically to the carbon surface as water passes through, becoming permanently trapped. The carbon doesn’t dissolve or release these compounds back into the water.

What Activated Carbon Removes

Activated carbon retains beneficial minerals (calcium, magnesium, potassium) — it selectively traps chemical contaminants while allowing minerals to pass through.

Carbon Block vs Granular Activated Carbon (GAC)

Carbon block: compressed carbon in a solid block. Water is forced through the entire block, maximising contact time and contaminant removal. Better performance at equivalent flow rates. Used in most quality under sink and benchtop filters.

Granular activated carbon (GAC): loose carbon granules in a housing. Water can channel through gaps between granules, reducing contact time. Lower cost; used in whole house systems where flow rate is the priority.

Frequently Asked Questions