Horizontal Roof Drain Pipe Sizing

Adequate drainage is an important component of a properly installed roof so installing the correct size of drains is essential.

Horizontal roof drain pipe sizing. Enter table 1108 2 until youfind a diameter pipe that will carry 4 688 sq ft. A minimum 5 inch diameter drain on a 1 4 inch per foot slope is required. For larger roof drains the pipe may be smaller such as a 10 in. The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain.

The roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g. To convert to an area for use in table 1108 2 do this. The result is the number of drains needed. Zurn plumbing products groupspecification drainage operation 1801 pittsburgh avenue erie pa 16502 phone 814 455 0921 fax.

Or 12 drains required. The maximum number of drainage fixture units connected to a given size of horizontal branch or vertical soil or waste stack shall be determined using table 710 1 2. For example a 4 in. Or less in diameter the piping will be larger in diameter than the roof drain.

For example in the u k. A 5 inch diameter pipe with a 1 4 inch per foot slope will carry 4 720 sq ft. Roof drain connected to an 8 in. Designers specify compliance with bs en 12056 3 2000 that includes a calculation for the allowable capacity of the rainwater pipes.

Roof drain vertical requirement for horizontal roof areas at various rainfall rates leader size hourly rainfall in inches pipe open 1 1 1 2 2 2 1 2 3 4 5 6 7 8 size area inches sq. The minimum size of any building drain serving a water closet shall be 3 inches. This means that because our horizontal pipe from step 3 was 8 our vertical pipe will be also 8. Roof drain connected to a 6 in.

5 000 4 x 3 75 4 688 sq ft. 1 inch 25 4 mm 1 inch per foot 83 3 mm m. In total square footage covered per drain 23 14 2 880 1 920 1 440 1 150 960 720 575 480 410 360. Section 101 5 of the ipc tells us not to reduce the pipe size in the direction of flow.

Take the roof s total square footage and divide by the total square footage handled by one drain. Following this logic it is possible that for roof drains 6 in.