Self-closing drain plugs with redundant sealing

A drain plug assembly, comprising:

• a valve body having a central bore extending between an inlet and an axially opposite outlet, the bore having a seat arranged between the inlet and the outlet of the valve body;
• a removable closure having a seated position and an unseated position, the closure being spaced apart from the seat in the unseated position, the closure abutting the seat in the seated position to form an outer seal fluidly isolating the outlet from the inlet;
• a poppet arranged in the bore on a side of the seat opposite the outlet and movable between an open position and a closed position, the poppet being spaced apart from the seat in the open position, the poppet abutting the seat in the closed position to form an inner seal fluidly isolating the outlet from the inlet;
• and
• a resilient member arranged between the inlet and the poppet, wherein the resilient member is configured to bias the poppet towards the poppet closed position to fluidly separate inlet from the outlet when the closure is in the seated and unseated positions.