A pipe, working at full speed, can fill an empty cistern in 1 hour. However, during the first hour it worked at one-twenty-fourth of its capacity, during the second hour at one-twelfth of its capacity, during the third hour at one-eighth of its usual capacity, during the fourth hours at one-fourth of its usual capacity and during the fifth hour it was only one-half as efficient as it was supposed to be. A second pipe also displayed similar performance, but if it worked at full speed would have filled the empty cistern in 2 hours. Together with a drain pipe that drained water out of the tank a constant rate, the empty cistern could be filled in 5 hours, all the three pipe working concurrently. How many hours will it take the drain pipe to empty the filled cistern if no other pipe was functioning during the time?