Around 3 trillion tons of ocean water is evaporated each day, much of it from the heat of the sun. The rate at which water evaporates depends on several factors.
Water is recycled in a process called the water cycle. This occurs as the Earth warms up. It becomes a vapor when the heat surrounds the ocean, lakes and other bodies of water. The vapor from the water rises up into the sky, where it turns into drops and then clouds. In time, the clouds may become overly heavy, and that is when precipitation occurs in the form of snow or rain. Either this will fall back into the bodies of water, or it will run along the streets and water table underground to go back into the oceans, streams and lakes eventually. In this way, the water always returns to vapor.
Water that is high up on a mountain can turn into snow easily. This will take a longer time to melt than it if were in liquid form. Water that goes under the ground into aquifers will take an especially long time to evaporate, since it is trapped underground until it is pulled up by someone. However, a drop of water in a body of water may evaporate and form rain within only a few days. There really is no way of knowing exactly how long it will take for the water to evaporate, since many factors are involved.