This invention relates to a fluid collecting system for collecting fluid downstream from a patient via a fluid collection line. The system comprises a fluid collecting bag (12) and an overflow device (14). The bag comprises an inlet tube (20) connectable to a bladder of a patient and to the interior of the bag (18), and an overflow tube (26) connected to the inlet tube (20) adjacent a top of the bag (12) and to an optional overflow device (14) to drain the bag if overflow occurs, in use. The overflow device (14) comprises a housing (30) having chamber (32), an inlet port (34) to the chamber connectable to the overflow tube (26), and a resiliently flexible member (36) located in the chamber. The member (36) is displaceable between a storage configuration, in which the overflow member is located in the chamber (32), and a filling configuration, in which the overflow member (36) extends from the chamber with fluid received from the overflow tube (26) held therein.
