Even the best tap water can have trace amounts of chemicals, pharmaceutical drugs and over-the-counter medicines lingering in it. That's why it's best to use a water filtration system when drinking tap water. But the same water that you and your family drink should also be used for your pets. Since hormone disrupters, chlorine, toxic metals and other particulates can come in unfiltered water, these things can also be damaging to your dog or cat. To make it easy, many pet stores now offer water-drinking systems that have integrated filters to always give your furry friends filtered water.