CV, why does her aunt believe she needs one? Most water treatment plants these days fully treat the water and in the many articles I've read there is very little difference in lab tests between tap and treated tap water.
With that said, my wife does use a Britta pitcher with filter in it that we keep in the fridge with cold water. However, I drink right out of the tap. Some nitrates and things are good for you.
I'd guess her concern is taste. As per my post above, I'm so used to untreated water that I simply can't drink the tap water here at work or in hotels or anywhere treated for that matter. Just like in a swimming pool, my bodies natural reaction to the taste of chlorine is to spit it out.
I'm glad they treat water in the cities, but when I travel, it's bottled for me.
