Which water filter is the best?

Earlier this year, I wrote about hexavalent chromium, a known carcinogen, in drinking water.  The most effective way for consumers to protect themselves from this chemical is a reverse osmosis water filtration system.

In order to remove the widest variety of environmental pollutants, the the Environmental Working Group (EWG) suggests using a filter that combines reverse osmosis with carbon filtration. Their website recommends four such systems.  As I am planning on buying a filter later this year, I decided to take a closer look at the systems listed by the EWG.  The first thing that I noticed is that their list may be somewhat out of date, with two of the systems currently out of stock.  The EWG is a non-profit organization and may not have the capacity to keep up with all the changes in this market, but I still think it is wise to buy the systems that they recommend.  According to the EWG, combined carbon/reverse osmosis systems often use poor quality carbon filters, and care should be taken when buying one. Look for a filter with certification from the California Department of Public Health or the National Sanitation Foundation.

The combined filtration systems recommended by the EWG are:

Bestwater Reverse Osmosis System II: 52345
Type: On-counter
Lifespan: 500 gallons
Price: $525.15 (2007)
Description: This counter-top water filter contains a reverse osmosis membrane as well as a pre-filter and post-filter made of activate carbon. The two carbon filters help to preserve the longevity of the reverse osmosis membrane and remove contaminants that the membrane can’t. The unit has an attractive, ergonomic design in white plastic that allows easy access for replacing filters.
Reviews: I could not find reviews of this filter on Amazon.com. On ConsumerDemocracy.com it received a score of 5 out of 5. This review stated that, compared to competing models, this system removes more contaminants and that the filter is easier to replace.

Multi-Pure MP750 Plus Reverse Osmosis System
Type: Under-sink
Lifespan: 750 gallons
Price: $629.95
Description: This system contains a pre-filter, a reverse osmosis membrane, and employs the Model MP750 carbon block filter as the post-filter.  Filtered-out material is flushed down the drain and the system requires no electricity.  The filters requires a cabinet-sized space beneath the kitchen sink, and connect to a small faucet that sits on the kitchen counter.
Reviews: I could not find a review of the combined filter but the Multi-Pure carbon filters received positive reviews on Amazon.com.

Watts Premier WP Reverse Osmosis System
Type: Under-sink
Lifespan: 600 gallons
Price: $249
Description: This system cleans water using a four stage process: 1.) A sediment trap removes large particles of dirt or debris from the water; 2.) a coconut shell carbon block pre-filter preps the water for reverse osmosis; 3.) a reverse osmosis membrane purifies the water; and 4.) a final coconut shell carbon block post-filter polishes the water. This system sits in a cabinet beneath the sink and discharges water through a chrome faucet that also contains an indicator showing when the filters need to be replaced.
Reviews: On Amazon.com, this system has a 4 out 5 star average based on 31 reviews. On the Watts website, it received a 3 out of 5 star average based on 11 reviews. Customers liked the system overall, but said that the faucet was poor quality and developed leaks over the three year warranty period.

Watts Premier RO-Pure Reverse Osmosis System
Type: Under-sink
Lifespan: NA
Price: Currently out of stock
Description: This filtration system uses a similar 4 stage process as the Watts Premier WP system.  The major difference is that filters have been designed to snap in and out very easily.  The water supply to the system does not need to be turned off before changing the filters.
Reviews: On Amazon.com, this filter has a 4.5 out of 5 star average based on 14 reviews. On the Watts website, this product has a 4 out 5 start average based on 44 reviews. Customers loved the water quality and said that the system was easy to install, but the faucet sometimes leaked water.