Filter types explained

“Water filter” covers a handful of very different technologies, each built to remove a different category of thing from your water. Picking the wrong one means paying for filtration you don't need.

Activated carbon

The most common household filter type (jug filters, under-sink, fridge filters). Carbon adsorbs chlorine, some pesticides, and compounds that affect taste and odour. It does not remove dissolved minerals or most heavy metals.

Reverse osmosis (RO)

Forces water through a semi-permeable membrane, removing a much broader range of contaminants: dissolved salts, nitrates, many heavy metals, and more. It also strips out beneficial minerals and produces some wastewater, so it's usually installed as a dedicated drinking-water tap rather than for the whole house.

Mechanical/sediment filters

Simple physical barriers that catch particles like rust, sand, and grit. Often used as a first stage ahead of carbon or RO filters to protect them from clogging.

UV filters

Use ultraviolet light to neutralise bacteria and other microorganisms. They don't remove chemicals, minerals, or particles, so they're typically paired with a sediment or carbon stage.

Ion exchange

Ion exchange is the technology behind water softeners: it swaps calcium and magnesium for sodium or potassium. Some countertop filters use a similar principle at a smaller scale.

Choosing one

Start with what you're trying to fix. Taste and chlorine → carbon. Broad contaminant reduction → RO. Hardness and limescale → softener/ion exchange. Sediment or discoloured water → mechanical pre-filter, usually paired with something else.