Water filter guides

How filtration actually works, without the marketing. These pages explain the mechanisms so you can work out what your water needs, rather than buying a product and hoping.

• How do water filters work?

  The six mechanisms — mechanical, carbon, ion exchange, reverse osmosis, UV and distillation — what each removes, what it misses, and why systems combine them.

• Do water filters remove fluoride?

  Carbon filters remove almost none. Reverse osmosis removes 85–95%, and three other methods work. The full comparison, plus how to check a certificate.

Looking for a recommendation instead? Best whole house water filter systems ranks the systems we score highest, and how we rate publishes the formula behind those scores.