Roof Drain Pipe Slope

The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain.

Roof drain pipe slope.

Roof drains for flat or low slope roofs come in a few standard types. A slope of less than 1 4 inch per foot will cause constant drain clogs and a slope of more than three inches will allow the water to drain without the solids. The term slope is also frequently used and has the same meaning as pitch. Vent piping allows sewer gases to escape the system and admits air to regulate the system s pressure and prevent siphonage from drain traps.

Calculating the slope of your drain pipe is easy. Drain pipe slope calculator. The best type for the application depends on several factors such as the size and slope of the roof the desired appearance and how much regular maintenance the drain system might need. This drain pipe slope calculator will calculate the slope and total drop fall of a drainage pipe over a specified length of pipe.

The secondary roof drains shall connect to a piping system in accordance with section 1101 12 2 2 1 or section 1101 12 2 2 2. The maximum height of the roof drains shall be a height to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by section 1101 12 1. The following diagram lays out the different terms that are used in the calculator. It is generally accepted that 1 4 per foot of pipe run is the minimum for proper pitch on a sewer line.

All of your drain pipe with one exception must slope slightly downhill. According to plumbing code drain pipe has to be sloped a minimum of 1 4 inch per foot and a maximum of three inches per foot or vertical. Drain waste and vent pipe hanger spacing support of drain waste and vent dwv pipes. Larger lines such as 8 pipe actually require less pitch due to the larger circumference of the pipe.

Usually 1 8 per foot is plenty for drainage this is the same as the commonly recommended 1 slope. I downloaded installed and tried out harmer drainage s free roof drainage calculator for a flat roof choosing a roof drain product line which has implications of drain pipe diameter and thus capacity geographic area the tool can plug in rainfall rates for the u k and i used an assumed a roof area of 10x10m 100 m2. But there are other issues concerning pitch to keep in mind. Note that i said the drain pipe must be sloped rather than the french drain.

While vent piping generally runs straight to the building s roof in a vertical path drain and waste branch pipes must slope toward main drainpipes which slope toward main drain outlets. Cleanouts in draining systems cleanouts provides access to the sewer for rodding.