How Water Filters Work

Filtration Methods

Different filters use different methods to remove contaminants. Most home filters combine multiple methods for comprehensive filtration.

1. Mechanical Filtration

The simplest method: water passes through a physical barrier that blocks particles. Think of it like a screen door keeping out bugs. Measured in microns—smaller micron ratings mean finer filtration.

• 1 micron: Blocks cysts like Giardia and Cryptosporidium
• 5 microns: Blocks most sediment and visible particles
• 50+ microns: Basic sediment pre-filtration

2. Activated Carbon Filtration

The most common home filtration method. Activated carbon (usually from coconut shells) has a massive surface area with millions of tiny pores. Contaminants stick to the carbon through a process called adsorption.

Removes: Chlorine, volatile organic compounds (VOCs), some pesticides, bad taste and odor.

Doesn't remove: Dissolved minerals, salts, fluoride, bacteria, viruses.

3. Reverse Osmosis

Water is forced through a semi-permeable membrane with pores so small (0.0001 microns) that most dissolved substances can't pass through. Removes up to 99% of contaminants. See our complete RO guide.

4. Ion Exchange

Used in water softeners and some filters. Exchanges unwanted ions (like calcium, magnesium, or lead) for less problematic ones (like sodium or hydrogen). This is how water softeners work—they exchange hardness minerals for sodium.

5. UV Disinfection

Ultraviolet light at 254nm wavelength damages the DNA of bacteria, viruses, and other microorganisms, making them unable to reproduce. Used primarily for well water or situations where biological contamination is a concern.

Important: UV doesn't remove contaminants—it only disinfects. Water should be filtered first to remove sediment that could shield microorganisms.

6. Distillation

Water is boiled, and the steam is collected and condensed. Contaminants are left behind. Very effective but slow and energy-intensive. Rarely used for home drinking water.

Comparing Filtration Methods

Method	Removes	Doesn't Remove
Carbon	Chlorine, taste, odor, VOCs	Minerals, fluoride, bacteria
Reverse Osmosis	Almost everything	Some VOCs (needs carbon stage)
UV	Bacteria, viruses, parasites	Chemicals, minerals, particles
Ion Exchange	Hardness, some metals	Bacteria, most chemicals

Why Multi-Stage Filtration?

No single method removes everything. Quality systems combine methods:

• Stage 1: Sediment filter (mechanical) — protects other filters
• Stage 2: Carbon filter — removes chlorine, taste, odor
• Stage 3: RO membrane or additional carbon — removes remaining contaminants
• Stage 4: Polishing filter — final taste improvement