Roof Drains Technical Data :: Overflow Drains

OVERFLOW DRAINS
Overflow drains should be specified to prevent the overloading of roofs where the building code calls for a specific maximum water build-up depth. This is where parapet scuppers are not used. Parapet scuppers have fallen into some disfavor because they create unsightly streaks on the building face. Certain codes call for the overflow system to remain independent of the primary leader system to the exterior of the building. In those systems the overflow drains remain inactive until the water level reaches the overflow level.	The exterior water dam type overflow drain, Fig. 1080, is usually preferred to the interior standpipe overflow drain, Fig. 1070, because the dam keeps debris away from the dome and accommodates more overflow drainage with less head build-up than the standpipe.
NOTE: Fig. No. 1070 and 1080 drains are special purpose drains used in conjunction with the conventional roof drainage system. These drains should never be used unless special structural and architectural considerations have been provided.
RAINTROL® ROOF DRAIN
Metered flow rate roof drains should be specified to control rainwater runoff from roofs where uncontrolled run-off would overburden storm drainage systems. Such control, with temporary retention of rainwater on the roof until the storm abates, provides relief for the drainage system. Roofs for which metered flow drainage is planned must be structurally designed to support and retain the rainwater load during the prolonged drainage period. Smith RAINTROL® metered flow rate roof drains are designed to provide this control. Sizing, quantity and location of RAINTROL® roof drains are separate and distinct procedures from those for regular roof drains.
VANDAL PROOFING
All roof openings, whether they are at the roof drain or at the vent stack, should be protected from vandalism. It is recommended that all vent stacks be furnished with vandal proof vent caps. Vandal proof roof drain domes and vent caps protect the roof leaders and vent stacks from vandalism prohibiting foreign objects being either carelessly or maliciously placed in the pipes. VANDAL PROOF VENT CAPS add to the finished look of any roof and are designed with a vent open area to pipe area ratio of 3 to 1.