In the event of an emergency, because your home may not maintain its usual easy access to potable water, FEMA and other government agencies recommend keeping a three-day supply on hand, just in case. Many homeowners decide to stockpile much more. However, no matter how much water you store in the basement or garage, there’s always the possibility of running out before the municipal supply returns to normal. To plan ahead for a situation in which you must source water in creative ways, consider investing in a household water purifier like the Big Berkey, a longtime favorite of both doomsday preppers and international aid organizations like UNICEF. Available at Amazon; $288.50.