Roof drain for effective drainage

If you’ve got the following points covered, you’ll be well-equipped to make the right choice and avoid having to change your mind along the way:

- Roof area and natural low points

- Roof pitch and construction

- Options for piping and penetrations

- Risk of clogging from leaves and debris

- Need for emergency drainage

Before placing your order, determine which type of well is suitable for the structure and whether you need accessories such as a grate or filter. This ensures that the solution is a good fit for the project from the start.

Emergency drainage serves as a backup in case the primary roof drain cannot keep up or the drain becomes partially blocked. An emergency drain is typically located higher than the primary drain, so that it is activated only when the water level rises.

Requirements and solutions for emergency drainage depend on the specific project, building type, and design. It is a good idea to discuss emergency drainage with a consultant or contractor before determining the number and location of outlets, to ensure that the backup drainage system functions as intended when the primary drainage system is overloaded.

On larger roof surfaces, a single drain is rarely sufficient. The layout should be based on the roof’s natural low points, and if the roof surface has several separate low points, it makes sense to place a drain at each of them. This reduces the risk of water pooling and lessens the load on individual drains during heavy rain.

Also consider capacity from the outset. An undersized well will struggle to keep up during heavy downpours, even if it is installed correctly. Therefore, determine the number, location, and size of the wells early in the project.

When water pools on the roof, it increases the load on the roofing material and joints. Over time, this can lead to leaks and moisture damage, and in the worst case, damage to the roof structure itself—damage that is both time-consuming and costly to repair. With a roof drain tailored to your roof’s conditions, you ensure continuous drainage and significantly reduce the risk of water accumulation.

Whether you’re planning a new roof or renovating an existing one, it’s a good idea to consider drainage early on. This ensures that the location of the roof drain and the piping align with the roof’s structure and other penetrations.

There are several solutions available, since roofs and piping are rarely identical. Here are the most common ones and what each is best suited for.  

Roof drain wells

Roof drain inlets are the standard solution with a vertical downward outlet. This type is ideal when the piping can be routed directly down through the structure, making it the most commonly used solution on flat roofs. Roof drain inlets are available in various sizes so they can be adapted to the roof area and the volume of water to be handled.

Angled well

An angle drain directs water out to the side at a 90-degree angle and is used when a vertical drain is not possible. Typically, space constraints, building design, or existing piping make the angle drain the right choice. It is particularly relevant when the drain needs to be directed toward a roof edge or a specific area of the building without requiring structural modifications beneath the roof surface.

Horizontal well

A horizontal drain, also known as a horizontal roof drain, has a horizontal outlet. It is typically used when the drain needs to run horizontally for a distance before descending. This is relevant in buildings where piping is planned to run through a wall or utility area. Here, it is important to ensure that the piping has the necessary slope. Without sufficient slope, there is a risk that water will remain standing in the pipes.

Vomit

Overflow channels are used for the rapid drainage of large volumes of water and are particularly useful where visible drainage is desired or where drainage points are located so that water is directed away without placing an unnecessary load on the main piping.

They typically come with a grate or filter that reduces the risk of leaves and debris getting into the drain. Choose a solution that allows for easy access for cleaning, especially if the roof is located near trees or other sources of falling leaves.