Abstract: A drain valve comprising: a head; and a cantilevered spring coupled at one end to the head and at an opposite end to a portion of a drain system such that when the cantilevered spring is biased to a normally closed position, the head obstructs a hole. In some embodiments, the drain valve is installed in an aircraft fire suppression system. In yet other embodiments, the cantilevered spring has a variable radius serpentine cross section.