Normally this tube is run to the nearest floor drain. Most furnaces drip a small amount of water. It comes from condensation. Check to see if there was a hose attached, if not, you may have to attach a clear poly tube to the end and run it to a drain. If there is no drain locally, you may have to install a small condensate pump. Little Giant makes a great one that pumps the water overhead to the nearest sink or floor drain.