Choosing the Right Roof Drain Pipe for Your Building

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Posted Oct 22, 2024

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Close-up of a plumber's hands installing steel pipes indoors, showcasing skilled manual work.
Credit: pexels.com, Close-up of a plumber's hands installing steel pipes indoors, showcasing skilled manual work.

Choosing the right roof drain pipe is crucial for ensuring the water flows smoothly and efficiently off your building's roof. The type of roof drain pipe you choose depends on the size of your building, with larger buildings requiring larger pipes to handle the increased water flow.

A key consideration is the slope of your roof, as a steeper slope requires a more robust roof drain pipe to prevent water from backing up. For example, a roof with a slope of 1:12 or greater may require a pipe with a diameter of at least 4 inches.

The material of the roof drain pipe is also important, with PVC pipes being a popular choice due to their durability and resistance to corrosion. However, PVC pipes may not be suitable for buildings with high water pressure, where metal pipes are a better option.

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Choosing the Right Drain

The type of roof you have is a key factor in choosing the right drain. The design and materials of your roof, as well as its pitch, will determine the type of drain you need.

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Credit: youtube.com, How do I choose the right drain pipe for my drainage system?

Roof drains are sized based on the surface area of the roof they'll be covering and the average hourly rainfall rate at the building location. The larger the roof area and the higher the rainfall rate, the more powerful the drain needs to be.

To choose the right drain, consider the volume of average rainfall and storm design criteria set by the local building code. The rate of drainage and overflow requirements also play a crucial role in selecting the right drain.

Here are some key factors to keep in mind when choosing a roof drain:

  • Type of roof—design and materials
  • Roof pitch
  • Volume of average rainfall and storm design criteria
  • Rate of drainage
  • Overflow requirements
  • Roof load
  • Drain locations
  • Additional features, such as vandal-proofing

Four Steps to Sizing

Sizing a roof drain is a crucial step in choosing the right drain for your building. To do this, you need to calculate the surface area of the roof that the drains will be covering as well as the average hourly rainfall rate at the building location.

The next step is to determine each roof area that will be served by a separate leader, which can be obtained from the pipe or drain manufacturer. This information will help you determine the number of drains required.

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Credit: youtube.com, How to Size a Home Drainage System

You'll also need to divide the roof area by the area for each leader to determine the number of drains needed. The larger the leader capacity, the fewer roof drains are needed.

Here's a simple formula to keep in mind: roof area divided by leader area equals the number of drains required. This will give you a good starting point for sizing your roof drain.

In general, roof drains are spaced equally and are located in low points of the roof or in any areas where water accumulates.

What Drains Do

Roof drains are designed to funnel stormwater from your roof and away from your building. This is crucial for both smaller and larger buildings.

For smaller buildings, roof drains can send water out onto the property where it can be absorbed by the grass. This is a great way to keep the surrounding area clean and free of debris.

Larger buildings often send stormwater into the city's stormwater system. This is a more complex process that requires careful planning and maintenance.

Cast iron is a common material used for roof drains in commercial buildings and large residential high-rises. Over time, cast iron can rust, leading to cracks and holes.

Get on Top

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Roof drains are designed to funnel stormwater from your roof and away from your building. They can be made out of cast iron, but over time that cast iron can rust, leading to cracks and holes.

For larger buildings, roof drains often send stormwater into the city's stormwater system. This can be a complex and potentially costly process if not properly managed.

Roof drains can be made up of a complete system of drains, pipes, fittings, and accessories. Filling out a flow calculation form can help define this complete system.

The BLÜCHER® EuroPipe stainless steel drainage pipework system is an integrated part of the siphonic roof drainage system. This system is made up of a minimal number of components, making it the easiest and fastest to install in the market.

The stability of stainless steel piping means additional support rails and brackets are not necessary. This results in the siphonic drainage system with the lowest total weight.

Stainless steel roof drains and accessories, like those from BLÜCHER, can be used for all types of flat roofs with bitumen or single-ply roof membrane.

Types of Roof Drains

Credit: youtube.com, Primary and Secondary Storm & Roof Drains.

Siphonic roof drains are a popular choice for flat commercial roofs because they offer faster drainage than other types of roof drains.

They work smoothly and require relatively little maintenance, making them a cost-effective option in the long run.

Siphonic drains can be connected to a single leader, reducing the number of drains needed and making installation easier.

Scuppers

Scuppers are popular for flat enclosed roofs, terraces and parapets. They consist of small holes cut in the side of the roof so that the water can drain out. Metal or rubber is typically used to flash the area around the hole so that water doesn’t cause damage.

Scuppers typically connect to a downspout to direct the water to an underground drainage system. In other instances, the scuppers protrude from the building and allow the water to fall into a prepared space such as a gravel drainage area, below.

You can check to ensure that your downspouts aren’t clogged periodically. All you need to do is do a quick walk around the roof and check the scuppers, removing any debris.

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Inner

Credit: youtube.com, Flat Roof Drains design and installation - the Ultimate draining system for flat roofs

Inner roof drains are used on flat roofs and include a low section or channel that collects water and feeds it into a concealed drain that leads to an underground drainage system.

They're hidden from view, which is a big advantage. Inner drains are resistant to freezing but can require careful maintenance to prevent problems.

One of the benefits of inner drains is that there are no unsightly downspouts and gutters seen from the outside of the building. And, there's little chance that pipes will freeze.

To clean them, check your roof several times a year, using all necessary precautions, and look for debris in the sieves. Remove any debris and replace the sieves, and check the status of the sieves to see if any replacements are necessary.

Siphonic Drain

Siphonic drains are a type of roof drain that utilizes siphoning as a drainage mechanism, allowing for faster drainage than other types of roof drains.

Credit: youtube.com, Zurn Roof Drains Siphonic Drainage Systems

They're commonly used on flat commercial roofs and can be connected to a single leader. This makes them a great option for large buildings with a lot of roof space.

Siphonic drains typically cost more than other drain systems, but they work smoothly and require relatively little maintenance. This makes them a good investment for building owners who want a reliable and low-maintenance roof drainage system.

These systems can handle more water than other types of drains because the siphoning force helps move the water, allowing for horizontal leaders instead of sloped pipes. This means they're a great option for buildings with flat or pitched roofs.

To clean a siphonic drain, you'll need to inspect the siphons themselves to check for debris pulled up against the screen and remove any that's there. This is a simple process that can be done with a gloved hand.

Related reading: Roof Insulation Flat Roof

Blücher Pipework System

BLÜCHER Pipework System is a popular choice for rainwater gravity systems. It's visually pleasing and has a long lifetime.

Credit: youtube.com, BLÜCHER Siphonic Roof Drainage Systems

The BLÜCHER EuroPipe system is the natural choice for gravity rainwater systems. It's designed to be used as outside downpipe and as piping system within buildings.

BLÜCHER pipework is made of stainless steel, which is non-combustible and has a low weight. This makes it a preferred system for multi-storey car parks.

The system has a low sound level, which is ideal for buildings where noise needs to be minimized. It also allows for large flow to be combined with low sound level.

BLÜCHER pipework can be considered part of the architectural impression of a building's interior. The stainless steel surface can be designed to be visually pleasing.

In multi-storey car parks, fire safety is important due to the flammable nature of cars filled with gasoline. BLÜCHER stainless steel push-fit piping is the preferred system for these types of facilities.

Frequently Asked Questions

Where do roof drains drain to?

Roof drains lead water into a system of pipes below the roof, which then discharge it into a gutter or downspout at the side of the building. This efficient drainage system helps prevent water accumulation on the roof.

Brett Cain

Senior Writer

Brett Cain is an experienced blogger with a passion for writing. He has been creating content for over 10 years, and his work has been featured on various platforms. Brett's writing style is concise and engaging, making his articles easy to read and understand.

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