Reverse Osmosis ("RO") filters most contaminants from water. It is one of the most effective forms of filtration. It gets plumbed under your sink and has its own spigot. Add a line to plumb to your fridge water, too. You can also opt to upgrade the faucet for a designer look. Add a post-calcite filter to replace minerals lost through the RO process. The 25GPD is the size we recommend for most families.