Types of Roof Drainage Systems

Roof drains are designed such that they carry water away from the roof to protect it. Using the wrong size of pipe for a roof drain will not yield the expected result. It can even create more problems than it solves.

Roof drains come in various shapes and sizes, and will vary on the roof and the building in which they are installed. When roof drains are designed and installed properly, they will still be needing regular maintenance to do the job well.

Before deciding on which drain your home designer will work with, consider the size of the roof, slope, and the location of drainage, inflow rate, safety requirements and the amount of rainfall.

How to Size Your Roof Water Volume.

Roof drains should be evenly spaced and located in low points of the roof or in an area where water usually accumulates.

To determine the size of your roof drain, the surface area of your roof where the drains will be covering must first be calculated and the rate of the average rainfall per hour where the project is located.

Next, determine the roof area each leader drained. This information could be obtained from the manufacturer of the pipe or drain. Divide the roof area by each leader to determine the required number of drains. Choose a leader (drainpipe) size big enough to take care of the volume of water to be drained over-the bigger the pipe, the fewer the roof drains required.

Siphonic Roof Water Drain

This type of roof drain is designed to operate at full capacity when the water is sucked from the roof into the drain at higher speeds compared to flat drains. These roof drains gives the designer room to specify a minimum number of roof drains and connect them to a single rain leader. The siphon roof drains uses the siphoning mechanism to drain water faster than any other type of roof drain. It usually costs more than a regular roof drain, but it works smoothly and doesn’t require much maintenance. This type of drain can be connected by means of horizontal rain leaders instead of having downward or sloped pipes.

Green Roof Water Drains

The new trend in roof drains is to replace the traditional roof with a green roof. Green roofs reduce transmission of noise, improves air quality and reduce heat inside the building. A green roof drainage system is made to accommodate the drainage while protecting the building structure with heavy waterproofing membranes. There are two types of green roofs: intensive and extensive.