Sign up to receive email updates, action alerts, health tips, promotions to support our work and more from EWG. You can opt-out at any time. [Privacy]


EWG’s UPDATED Water Filter Buying Guide

Find the right filter for your water – and budget

Frequently Asked Questions

February 27, 2013

EWG’s UPDATED Water Filter Buying Guide: Frequently Asked Questions

EWG's Water Filter Buying Guide

How to choose a filter system that meets your needs

Q: Why didn’t you include X filter?

Answer: EWG chose to include all filters that were both certified by the California Department of Public Health and were available on so we had confidence that they were both effective and widely available. We also included information about NSF certification for these filters to provide consumers extra information. If you know of a water filter that you do not see in the database, it is because the brand/model is not certified by the California Department of Public Health to reduce one or more contaminants, or the brand/model is certified by California but was not available on

In order to comply with California law, when a manufacturer claims that a drinking water treatment device will reduce contaminants or makes other health related performance claims, the device must be certified by the California Department of Public Health if the device is to be sold in the state and be compliant with state law.  More information about California’s certification program is available here.

Q: Why don’t you have an option to filter out X contaminant?

Answer: There are two possible answers to this question. The first is that EWG does have an option to filter out the contaminant that you are interested in, but you are not looking in the right place. If you go to the bottom of the page and click on the “see more contaminants” link right above the search button, you will be provided with a much more extensive list of contaminants to choose from. It is likely that the contaminant you are interested in can be found on this list. If it is not, this is because there is no filter that was both certified by the California Department of Public Health and available on that is certified to reduce this contaminant as of February 2013.

Q: Why don’t you address effectiveness of the filter? This isn’t a buying guide!

Answer: Water filters vary widely in quality and in what contaminants they will reduce. Consumers need to do their research to make sure they are getting what they are paying for. There are many, many different kinds of water filters with many pros and cons. There is no single best water filter for everyone. EWG's guide is designed to help steer people through the complicated process of choosing the best water filter for them, depending on what contaminants are in their water and what they are most interested in reducing. We cannot give each filter a single rating because the efficacy of the filter will depend on what contaminant you are trying to filter out. In addition, there are other factors such as cost, energy use and water use that also vary between different filter types, but are more important to some consumers than others. 

Q: What's the best water filter?

Answer: There isn't any single best answer to this question. Carbon filters remove fewer contaminants than reverse osmosis filters, but are cheaper and use less energy and water. Reverse osmosis filters are more effective at removing many kinds of contaminants, but are more expensive, require more maintenance, and require much more energy and water to function. Water softeners are great for dealing with hard water problems, but won't remove most contaminants. It's really a personal decision as to what water filter is best for you and your family.

Q: Why do you have links to Amazon and not to small businesses?

Answer: For the sake of simplicity, EWG chose to feature just one on-line retailer where consumers could easily buy water filers. We chose because of their wide range of available filters and because EWG participates in the Amazon affiliate program. While EWG, of course, fully supports consumers buying water filters from small businesses and any retailer of their choice, we also realize that many consumers are looking for the convenience that large on-line retailers such as provides. Via the Amazon affiliate program, EWG gets a small donation for every purchase made on Amazon through our website link.  EWG’s aim is not to get people to buy water filters from, but rather to make it easy for people to choose and buy the right water filter for them.

Q: I have a water filter company, how can I be included in your guide?

Answer: EWG’s water filter guide contains filters that are both certified by the state of California to reduce one or more contaminants and are available on To be included in future versions of this guide, EWG recommends getting your company’s filters certified by the state of California and making your company’s products available on Information about the California Department of Public Health certification process is available here