Used on flat roofs of any construction (other than poured in place) where an emergency overflow drain can be used in combination with a standard roof drain. Large sump drain bodies with low profile domes provide sufficient free area for quick drainage of rainwater while protecting the drain sump and connected piping from the intrusion of debris. Internal standpipe type overflow drain receives water only when the build-up is greater than the setting of the standpipe. Water dam standpipe can be cut to achieve various water depths on the roof. Attached wide dual drain deck plate with securing holes enables both drains to be secured to the roof deck from the top surface of the roof reducing installation time, reducing the number of roof penetrations and eliminating the need for an underdeck clamp. The wide dual deck plate also recesses the drains slightly to prevent water build-up at the base of the drains.