Roof Drain Pipe Size

Or 12 drains required.

Roof drain pipe size.

We regularly get asked about the water flow capacity of different pipe sizes and which is the best roof drain for a specific pipe size. When sizing roof drains the limiting factor for the amount of water each drain will carry away is the size of leader therefore increasing leader size decreases the number of drains required. Roof drain connected to a 6 in. 300 x 500 150 000 sq.

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. The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain. Enter table 1108 1 until you find a diameter pipe that will carry 2 344 sq ft. Each vertical drain must carry 2 500 sq ft of roof area at 3 75 inches per hour of rainfall.

This reveals that the minimum size for the leader pipe is 5. Following this logic it is possible that for roof drains 6 in. Pipe size in inches vertical drain gpm 1 16 per foot gpm 1 8 per foot gpm per foot gpm per foot gpm 2 34 15 22 31 44 3 87 39 55 79 111 4 180 81 115 163 231 5 311 117 165 234 331 6 538 243 344 487 689 8 1 117 505 714 1 010 1 429 10 2 050 927 1 311 1 855 2 623 12 3 272 1 480 2 093 2 960 4 187 15 5 543 2 508 3 546 5 016 7 093. The first step in sizing a roof drain is to calculate the surface area of the roof that the drains will be covering as well as the average hourly rainfall rate at the building location.

Step by step sizing of zurn drains step 1. A minimum 4 inch vertical drain is required. For example a 4 in. Roof drain connected to an 8 in.

Section 101 5 of the ipc tells us not to reduce the pipe size in the direction of flow. Sizing a roof water drain. Unfortunately recommendations aren t that straightforward because you also need to account for water pressure material friction and more. The result is the number of drains needed.

Therefore the 100 000 sq. 50 000 4 400 11 36. Take the roof s total square footage and divide by the total square footage handled by one drain. Calculate total roof area.

Or less in diameter the piping will be larger in diameter than the roof drain. 2 500 4 x 3 75 2 344 sq ft. 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. To convert to an area for a 4 inch per hour rainfall to enter table 1108 1 do this.

Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq. For larger roof drains the pipe may be smaller such as a 10 in. Roof area is 300 x 500 ft. Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage.