Roof Drain Pipe Design

The flow rate used for sizing the storm drainage piping shall be based on the maximum anticipated ponding on the roof.

Roof drain pipe design.

Cast iron roof drain with 2 in. The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain. A minimum 5 inch diameter drain on a 1 4 inch per foot slope is required. Buried or underground roof drainage downspout defects clogging overflowing holes corrosion leaks that cause wet basements or crawl areas proper installation of buried downspout extensions proper installation of french drains seepage pits at flat sites gutter downspout defects cause wet basements crawl areas questions answers about installing maintaining repairing buried roof.

Take the roof s total square footage and divide by the total square footage handled by one drain. Section 101 5 of the ipc tells us not to reduce the pipe size in the direction of flow. Rd rd 10 000 4 x 3 75 9 375 sq ft. The roof drainage outlets and rainwater downpipes are calculated based on the design principles for gravity drainage systems established in ss525 2006 code of practice for drainage of roofs.

This reveals that the minimum size for the leader pipe is 5. 1 8 1 4 and 1 2 per foot. If you need help finding a drain ask our drain wizard or call to speak with our roof drain expert. Pipe sizing is listed as amount of square foot roof areas served by the drains.

Or 12 drains required. A 5 inch diameter pipe with a 1 4 inch per foot slope will carry 4 720 sq ft. Watts drainage products rd 300 r series 4 in. Code tables outline pipe slopes of.

50 000 4 400 11 36. According to the chart for 1 8 slope per 12 of pipe for 5 000 square feet of roof area with a 6 per hour of rainfall the required pipe size is 8. Section 1105 roof drains 1105 2 roof drain flow rate. Use this downspout extension to divert water away from the foundation or connect to drainage pipe and catch basin to control drainage.

Different horizontal sloping will offer different drainage capacities. Enter table 1108 2 until you find a diameter pipe that will. To convert to an area for use in table 1108 2 do this. To size the vertical roof drain for the same parameters 5 000 square feet of room area and 6 per hour of rain consult table 1106 2 figure 3.

Horizontal drain 10 000 sq ft. The flexible design easily bends and holds its shape and can be extended from 25 in. We also stock many of the top selling drains and parts onsite so most orders ship same day. But this isn t the whole story.

Hy tech is an authorized distributor of all roof drain manufacturers so you can find what you need when you need it.