Roof Drain Sizing

The four things you will need to know are.

Roof drain 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. The result is the number of drains needed. Factors which affect proper roof drainage are deck slope drain size and placement of drains. And then determine from the chart below how many roof drains you require.

For the purposes of this appendix the following metric conversions are applicable. 50 000 4 400 11 36. Roof water drain types and sizing sizing a roof water drain. And 4 area handled by each drain.

The sizing of roof drains must be large enough to quickly carry away all water entering the roof drains. How to measure roof drain parts. 2 total area of roof. Conventional gutter systems such as those used on most houses are suitable for some low slope roofs.

1 rate of precipitation. The sizing of the roof drainage system must consider all components. The full flow capacity of a drain is not realized until the water reaches approximately 2 5 above the inlet in a four inch drain and 3 5 in a six inch drain. For example in the u k.

Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq. Product name manufacturer color bolt hole style lip to lip bolt to bolt 180 bolt to bolt bolt holes type of bolt used material. The roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g. Or 12 drains required.

Take the roof s total square footage and divide by the total square footage handled by one drain. 3 size of leader required. Therefore the 100 000 sq. Zurn makes it easy to size roof drains.

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. Designers specify compliance with bs en 12056 3 2000 that includes a calculation for the allowable capacity of the rainwater pipes. Roof drain system and size the scuppers denoting the required head of water above the scupper for the structural engineer. 1 in 25 4 mm 1 ft 305 mm 1 ft2 0 0929 m2 100 0 figure a101 1 example roof plan 4 a 101 2 solution.

The rain storm the flow of rainwater on the roof surface the ability of the roof drain to move the water from the roof to the piping the vertical piping the horizontal piping and the connection to the point of discharge. 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.