Water filters and water treatment systems are designed to reduce a wide range of contaminants such as heavy metals, chemicals, pesticides, chlorine by-products, and disease-causing microbes, which have adverse health effects. Using effective water filters and systems can help reduce these dangers in water supply. There are many different types of water filters and water treatment systems, ranging from whole house purification systems to countertop or refrigerator pitcher filters for drinking water, and from reverse osmosis purification to a simple charcoal fiter. It’s a good idea to have a household's water tested, whether it comes from a municipal source or a well, to determine what type of filtering system will best serve the home's needs.