Topographic features like ridges and islands, such as the Greenland-Iceland-Scotland Ridge (GISR), can obstruct drainage from a deep ocean basin. If the flow in connecting straits is hydraulically controlled, the drainage depends on the conditions in the draining straits as well as the upstream conditions. Importantly, through upstream influence imposed by hydraulic control the draining straits feed information to the upstream basin using long waves to maintain certain constraints on the upstream flow through the controlling sill. However, the impact of hydraulic control on the transport of dense water masses through straits, its relationship with strait geometry, and the interplay between multiple draining straits through long waves remains unclear. This study focuses on investigating the draining time scale of a deep basin through Kelvin waves interacting with one or two hydraulically controlled sill flows. To conduct this research, we employed an idealised 1.5-layer reduced-gravity model featuring two basins connected by one or two straits. When the generated Kelvin wave encounters hydraulically controlled flows in the straits, it is partially reflected back to the upstream basin. The strength of this interaction determines the draining time of the basin. This study explores how the draining time is impacted by the presence of a second strait, their location, their geometry and the water properties. The findings of this research contribute valuable insights into understanding the communication of long waves between multiple draining straits subject to hydraulic control. Additionally, the results are discussed in the context of the GISR.@en