The cheapest drinking water filter is probably the basic activated carbon filter, like Pur faucet filters. The filter connection is in the $30 range, the filter replacements about half that price. These filters work by forcing water through an activated carbon filter. The activated carbon attaches itself to different impurities in the water, holding them in the filter while the purified water continues on. These filters are primarily to filter out living contaminants like cryptosporidium and bacteria, though they also filter out some inorganic contaminants. Minerals stay in your water.

To eliminate serious contaminants such as lead or high chlorine levels, a reverse osmosis drinking water filter is probably your best bet. These complex but ingenious devices can be installed right under your kitchen counter. Working with a filter that allows only pure water to pass, they slowly eliminate toxins from your tap water, holding purified water in a reservoir that you access through a separate tap on your sink. Though these filters work slowly, they can provide plenty of drinking water for your family each day, even filtering salt from ocean water and eliminating most biological contaminants as well. These filtration devices use as much as ten gallons of water for every single gallon of drinking water they provide, so they aren't ideal for every household.

Using a reverse osmosis drinking water filter gives you plenty of bottled-water-quality drinking water for about five cents a gallon in most places, a significant cost savings when you consider what you pay for it at your supermarket. Water that is flushed from the system is still pure enough to spray on your garden and lawn, so if you have gray water storage there is no waste.

Though it's not quite a drinking water filter, you may have an ultraviolet filter added at the end of your reverse osmosis water filter, particularly in places that have contaminated water. A good UV filter will destroy any living contaminants, ensuring that your supply of water is as clean as possible. So the best reverse osmosis water filters actually have three different filters in a series to ensure the purity of your drinking water supply.

Ceramic filters are a type of drinking water filter that use diatomaceous earth, a natural silicon filter commonly used in commercial water treatment. This filter works similarly to an activated carbon filter, capturing your contaminants before they reach your faucet, and the resulting water is at least as good as that from an activated carbon filter.

Your perfect water filter depends on your tastes and budget. Spend a lot on bottled water? The osmotic is probably for you. Just want to filter out your tap water? A ceramic or carbon drinking water filter will probably be just fine.