Your annual water quality report or a state-certified home test can tell you what’s in your water. Thinking it’s easier to just switch to bottled water? There’s no guarantee that it’s safer than tap water. And bottled water comes with a cost both to your pocketbook and the environment. A home filter makes more sense, but finding the right one takes some research.

Here are two websites to get you started on your search. (Scroll down to see our chart on popular filters and what they remove.)

NSF. It certifies filters for their ability to remove specific odors, off-flavors, and contaminants. But its website is hard to navigate. To start, you can select a contaminant and filter type. The “Claim” column on the far right lists all the contaminants that the filter reduces or removes.

Water Quality Association. The website of the water-treatment industry’s trade group lists fewer filters, but it’s easier to navigate. Search by manufacturer if you have a filter in mind. Or select “filters” in the product category and the contaminants you’d like to filter out from the drop-down menu.

Types of water filters

Pitcher filter

• What is it: Water drips through a filter into a reservoir that can be refrigerated
• Pros: Inexpensive, easy to use
• Cons: Impractical if your household uses a lot of water; typically removes or reduces fewer contaminants than other filter types

Countertop filter

• What is it: Attaches to your faucet by a tube and sits on countertop
• Pros: Requires no extra plumbing
• Cons: Doesn’t fit all faucets; flow rate may be slow; can clutter countertop

Undersink filter

• What is it: Water passes through a filter that is plumbed in beneath the sink
• Pros: Filters a high volume of water with a high flow rate
• Cons: May require custom plumbing or alterations to sink or countertop

Reverse osmosis filter

• What is it: Forces water through several membranes to remove contaminants. It can treat the whole house’s water or can be installed under the sink to treat the kitchen’s water
• Pros: Removes the most contaminants, including arsenic and nitrates; good for severe water contamination
• Cons: Slow; requires custom plumbing and extra space; may create 5 gallons