Roof Gutter Drain Pipe Size

Designers specify compliance with bs en 12056 3 2000 that includes a calculation for the allowable capacity of the rainwater pipes.

Roof gutter drain pipe size.

For example in the u k. 5 inch 5 520 square feet. Now it is very bad practice to reduce a pipe size downstream. 6 inch 7 960 square feet.

For example a 4 in. Digging a trench that deep is only practical when the end of the pipe drains into a dry well or is connected to an existing drain line. For larger roof drains the pipe may be smaller such as a 10 in. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

If a roof s various drainage areas call for different size gutters go for the biggest one k style. And as such does not flow full. A down pipe size is more dependent on the perimeter of the pipe circular weir or orifice at the entrance than the cross sectional area. The flexible design easily bends and holds its shape and can be extended from 25 in.

Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. Roof drain connected to a 6 in. Whereas the underground pipe maybe flowing full thereby resulting in a smaller pipe. Featuring durable vinyl construction this extension can be buried bent or connected to additional sections.

The only guaranteed way to keep the pipe from freezing is to bury it below the frost line which ranges between 32 and 48 inches in most areas of the snow belt. 5 inch 5 520 square feet. Then use the information below to see what size gutter you need. Size downspouts to fit the gutter.

Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Smacna s new downspout and gutter sizing calculator enables the user to manually enter the design area of the roof or use the design area wizard for the calculation. Lay out the pipe lengths and fittings. This wizard makes it easy to calculate the roof design area by providing various shape calculations and the calculation for vertical walls area per international plumbing code ipc.

Roof drain connected to an 8 in. The downspout size must suit the bottom width of the gutter. Or less in diameter the piping will be larger in diameter than the roof drain. Multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.

Then use the chart below to see what size gutter you need. If a roof s various drainage areas call for different size gutters go for the biggest one k style. The gutter outlet capacity should suit the downspout capacity. The roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g.

Offset of more than 10 ft 3 0 m can affect drainage capacity. Doubling the number of downspouts halves the required capacity for each.