Now to take this further, I will describe each a bit.
The Pitcher filter is great if you just want to drink a good glass of clean water and are really not worried about the tap water for anything else in your home. With these you have a specially made pitcher with a filter at the top and you have to pour water in slowly and it filters this through to the bottom of the container. It may take 10 minutes or so for this to complete its process.
The Faucet filter I have found to be very popular, especially with families who have children. This attachment hooks up to the faucet spout and you have the choice to turn the filter on to dispense cleaner water or turn it off if you do not want to waste the cleaner. The only issue some families did not care for was that the pressure coming from the tap is diminished because it must go through the filter and process before coming out so I would say you get half of the pressure. Also it is a bit cumbersome and takes up space around the faucet and is a little unsightly if you are wanting a kitchen that looks designer beautiful.
The Refrigerator filter is becoming more popular as families purchase refrigerators with water and ice dispensers on the door. This hooks up inside the door and helps produce better tasting ice as well as water.
Under sink filters are great to have as a full kitchen use. It keeps clutter from being on top of the counter or faucet, however, it usually required a professional installation and you will have to give up some room under your sink cabinet to make space for this larger item.
The Shower filter basically allows you have have a bath free of contaminants. These are less common and people will usually get a whole house filter if they want good water in their bathrooms.
The Laundry Filter again is like the shower model information in that the whole house choice will usually be used. However, families find that they like to use cleaner water free from hard water deposits on their clothes.
The whole house filter is the next big upcoming appliance that families are automatically having installed in their homes when they are building a new home. It is somewhat of a no brainer that they can have great water and why not do it now while they are installing everything else.
