If you live in or near a large U.S. city, look it up on the Environmental Working Group database. Otherwise, you may need to contact your water utility and ask for a water quality report, or ask a local environmental group focused on water issues.
 Once you know the specific chemicals you are trying to filter out, you can read the packaging or online descriptions of water filter products to see whether they are removed. Alternatively, use the EWG filter selection search, or narrow down your options using these tips:Charcoal (or "carbon") filters are cheap and widely available. They will filter out most organic contaminants, including lead, mercury, and asbestos.
Reverse osmosis filters remove inorganic contaminants such as arsenic and nitrates. They are extremely water-inefficient, so use only if you know the water is contaminated with a chemical carbon does not filter out.
De-ionizing filters (or ion exchange filters) remove minerals, turning hard water into soft water. They do not remove contaminants.
 There are many types of water filters on the market, designed to accommodate a variety of needs. Here are the most common options for home use:A pitcher water filter. These are convenient for households with low water use, as you can fill the pitcher once or twice a day and keep it cool in the refrigerator.
A faucet-mounted filter is convenient if you want to filter all your tap water, but can slow down flow rate.
On-counter or under-sink water filters required plumbing modifications, but generally use longer-lasting filters, and thus require less maintenance.
Install a whole-house water filter if your water is severely contaminated and unsafe even for bathing.
 Each filter should come with a set of instructions showing you how to set it up so that it works correctly. In most cases assembly is quite simple, but if you have trouble putting it together, call the manufacturer for help.
 Take cold water and pass it through the filter. In most cases the water is poured into the top of the filter; it then makes its way down through the filter mechanism, where impurities are removed. The clean water streams into the bottom of the bottle or pitcher, or out of the bottom of the faucet, depending on what type of filter you have.


Do not submerge the filter while running water through it. Water that backs up into the filter may not be purified.
Some filters are damaged by hot water; check the manufacturer's instructions.
 After a few months of use, a carbon water filter becomes clogged and stops working as well to purify water. Buy a new filter cartridge from the same manufacturer that made the water filter. Remove the old cartridge and discard it, then replace it with the new one.


Some water filters last longer than others. Check the instructions that came with your product for a more detailed time frame, or contact the manufacturer.
Find out which contaminants are in your water.
Choose a type of filter.
Select an installation type.
Set up the filter according to the manufacturer's instructions.
Run water through the filter.
Change the filter cartridge as recommended.
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