US Patent 10227781 Drainage system and apparatus for treating runoff

A drainage system, comprising a collector which is arranged to collect liquid and a drainage pipe having a pipe inlet that opens into the collector such that liquid collected by the collector drains through the pipe inlet. The drainage pipe is provided with a vent spaced away from the pipe inlet. The vent is arranged such that, when liquid collected by the collector occludes the pipe inlet, liquid flowing through the drainage pipe draws air into the drainage pipe through the vent.