The Flat Roofing Shop
GRP Internal Drain Outlet – 50mm, 75mm, 82mm & 100mm
GRP Internal Drain Outlet – 50mm, 75mm, 82mm & 100mm
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Vertical Roof Outlet for Fibreglass GRP Roofing Systems
This GRP Internal Drain Outlet provides a secure vertical connection between a fibreglass roof and the rainwater downpipe below.
Designed specifically for GRP roofing systems, the outlet features a durable rigid pipe body with an integrated mesh flange, allowing the laminate to bond directly into the drainage detail for a seamless watertight finish.
Available in 50mm, 75mm, 82mm and 100mm options to suit standard downpipe sizes.
Important – Choosing the Correct Size ▸
The size selected refers to the downpipe size the outlet will fit into, not the diameter of the outlet itself.
The outlet spigot is slightly smaller than the named size to ensure a snug and secure fit inside the corresponding pipe.
Example:
Selecting 50mm means the outlet is designed to fit into a 50mm downpipe.
What It’s Used For ▸
- Forming internal vertical drainage points in GRP roofs
- Connecting roof deck to rainwater downpipe
- GRP outlet details in box gutters
- Replacing or installing new internal outlets
- Detailing balcony and flat roof drainage
Suitable for use in traditional GRP fibreglass & Flexitec roofing systems.
Why Proper Drain Detailing Matters ▸
Drain outlets are one of the most critical points on any flat roof.
Poor detailing can lead to:
- Water tracking beneath the laminate
- Leaks at pipe connections
- Movement failure around the outlet
The integrated mesh flange allows the base resin and CSM to fully encapsulate the flange, creating a secure mechanical bond within the GRP system.
Once laminated and top coated, the outlet becomes fully integrated into the waterproof membrane.
Installation Overview (GRP System) ▸
- Cut the deck opening to suit the outlet body.
- Insert the outlet through the deck.
- Mechanically secure if required.
- Laminate over the mesh flange using base resin and CSM reinforcement.
- Consolidate fully to remove air pockets.
- Apply top coat as part of the system finish.
Ensure correct falls are formed to direct water towards the outlet.
Technical Specification ▸
- Available Sizes: 50mm / 75mm / 82mm / 100mm
- Outlet Length: Approx. 200mm
- Material: Rigid GRP-compatible body with mesh flange
- Application: Internal vertical drainage
Roofer’s Perspective ▸
Drain details need to be right first time. A proper GRP outlet with a mesh flange laminates in cleanly and avoids awkward detailing around pipe penetrations.
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