Abstract: Embodiments include controlled flow rood drains which minimize the size of drainage piping and meet established maximum flow rates by draining built-up water from a flat roof. Embodiments are pre-set by the manufacture in terms of the diameter of the standpipe orifice, which controls maximum flow rate at a predetermined depth of water on the roof, and the height of the standpipe, which determines the depth of water on the roof. Embodiments resist alteration of the flow rate by vandals, tenants, or managers of the building, and are resistant to flow which bypasses the drain control and resistant to plugging by roof debris or snow.