If you see the drain in a dream, then it shows the necessity to let go the unfavorable feelings you are keeping within yourself. You should not be afraid to release the pain from time to time. On the other hand, the drain could symbolize the time and effort you have put into something that is useless. You should also look around and realize if there is anyone in your life that is draining your energy.
Read more about dreaming of Drain in other dream meanings interpretations.