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P-1106.1 General. The size of the vertical conductors and leaders, building storm drains, building storm sewers and any horizontal branches of such drains or sewers shall be based on a the 100-year hourly rainfall rate of 4.5" per hour. indicated in Figure 1106.1 or on other rainfall rates determined from approved local weather data.
1. Existing building storm drainage systems without secondary roof drainage installed in accordance with Section 1108 shall be designed based on a rainfall rate of 6" per hour.
2. The size of building storm drainage systems serving green roof systems, approved by the Philadelphia Water Department, shall be based on a rainfall rate of 3.1" per hour.
(Delete Figure 1106.1)
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