Purpose Of Roof Overflow Drain

We have seen engineered drawings showing overflow drains connecting to the same storm line albeit further down the line but still on the same drain.
Purpose of roof overflow drain. The drain may be used to redirect water after it reaches a certain level or serve as a means of effectively maintaining a certain level of any type of liquid in place as part of the manufacturing process. By the 1997 edition of the upc section 1101 11 2 had been added that completely prescribed where and how secondary roof drainage was to be provided. Flat roofs that do not drain over the roof edge and roofs that have parapet walls must utilize roof drains to get the water off the roof. If a blockage occurs after the connection to the overflow drain the overflow is useless and defeats the purpose.
Combination main overflow drain commercial construction commercial multi family thin wall construction. The 2006 international residential code specifies the size and locations for overflow drains on residential structures. An overflow drain is also used in manufacturing plants and other commercial assembly operations.