Provided are a drainage device with which the timing of drainage can be controlled; and a drainage system equipped with the same. The drainage device comprises a siphon mechanism that is provided inside a water tank and that constitutes a siphon pipe and a cylindrical part. One end side of the siphon pipe has a first opening part that is open at the top part thereof, and the other end side has a first connection part that is connected to an overflow pipe. The cylindrical part has a second opening part of which the inner diameter is larger than that of the siphon pipe into which the first opening part of the siphon pipe is inserted, and which is open at the bottom part thereof. The second opening part is set at a position lower than the first opening part and a second connection part.

Provided are a drainage device with which the timing of drainage can be controlled; and a drainage system equipped with the same. The drainage device comprises a siphon mechanism that is provided inside a water tank and that constitutes a siphon pipe and a cylindrical part. One end side of the siphon pipe has a first opening part that is open at the top part thereof, and the other end side has a first connection part that is connected to an overflow pipe. The cylindrical part has a second opening part of which the inner diameter is larger than that of the siphon pipe into which the first opening part of the siphon pipe is inserted, and which is open at the bottom part thereof. The second opening part is set at a position lower than the first opening part and a second connection part.

A double-bell siphon for liquid flow control that improves upon existing bell siphons by the addition of an outer bell which helps the bell siphon to stop siphoning when the liquid level drops below the intended level. Optionally, a cup further enhances the ability for the siphon to stop properly.

A double-bell siphon for liquid flow control that improves upon existing bell siphons by the addition of an outer bell which helps the bell siphon to stop siphoning when the liquid level drops below the intended level. Optionally, a cup further enhances the ability for the siphon to stop properly.