Horizontal Roof Drain Pipe Sizing

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.

Horizontal roof drain pipe sizing.

The roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g. Calculate drains needed. Enter table 1108 1 until you find a diameter pipe that will carry 2 344 sq ft. To convert to an area for use in table 1108 2 do this.

2 500 4 x 3 75 2 344 sq ft enter table 1108 2 until you find a diameter pipe that will carry 2 344 sq ft. Sizing a roof water drain. The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout. Size horizontal storm drainage piping.

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. The above sizing data is offered as a guide only. Take the roof s total square footage and divide by the total square footage handled by one drain. Designers specify compliance with bs en 12056 3 2000 that includes a calculation for the allowable capacity of the rainwater pipes.

The flow rate in storm drain piping shall not exceed that specified in table 1106 2. 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. 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. In a roof drainage system you have many components.

Horizontal drain 2 500 sq ft. Roof area is 300 x 500 ft. The required pipe size is 8. Storm drain pipe sizing.

Calculate total roof area. That is what is wrong. But this isn t the whole story. 300 x 500 150 000 sq.

A minimum 4 inch vertical drain is required. Zurn plumbing products groupspecification drainage operation 1801 pittsburgh avenue erie pa 16502 phone 814 455 0921 fax. Step by step sizing of zurn drains step 1. This reveals that the minimum size for the leader pipe is 5.

The result is the number of drains needed. The sizing of the roof drainage system must consider all components. For example in the u k. Vertical and horizontal storm drain piping shall be sized based on the flow rate through the roof drain.

The pipe sizing is only one component.