A horizontal sliding wall system includes a ceiling guide with at least one running track as well as at least one door leaf element, which is connected to a roller carriage, which is disposed in the ceiling guide to be displaceable. The horizontal sliding wall system includes a drainage rail recessed and flush-mounted with the building floor, which rail is disposed essentially aligned below the displacement path of a door leaf element. The drainage rail includes a first drainage profile and at least one second drainage profile as well as a first insulating web and at least one second insulating web. The first and second drainage profiles are fixed to be spaced apart from each other by means of the first and second insulating webs.