Filters remove chlorine, heavy metals, odors and other impurities. Depending on their prey, carnivores such as dogs (and especially cats) have evolved to filter their food form toxic materials. Furthermore, they are exposed to synthetic preservatives such as BHT and BHA in their foods, prescription drugs, environmental air and ground toxicity, as well as chlorine and other chemicals contained in tap water. The liver's ability to neutralize all these toxic materials is exceeded. The beautifully designed PURE WATER TOWER effectively removes chlorine, heavy metals and suspended material from the water at pennies per day. It's also a fraction of the cost of electric models.