People concerned about the quality of their water have a number of tests at their disposal. Lifehacker reports that, although such tests offer an idea of the nutrients in your water, "you should never base the cleanliness of your water on test strips alone. Talk to a professional that understands the chemistry of the water and how all the different factors interact to come up with water treatment options."
The First Alert WT1 Drinking Water Test Kit is readily available online. According to Lifehacker, it costs roughly $15 and can test for bacteria, nitrates, hardness, and lead. The tests don't check for every harmful contaminant, though, Lifehacker reports, so they're not entirely accurate.
WaterFilters.NET offers a home-testing kit for about $26 from Sensafe. The kit provides two tests, which look for iron, copper, chloride, nitrates, nitrogen, and more. It also includes a separate test for bacteria.
The PurTest White Water Test Kit costs roughly $26 and looks for 11 contaminants in three tests, one for bacteria, lead, and pesticides; the other two for copper, iron, nitrates, and more.