Internal roof drains are one of the highest risk failure points on flat roofs. If water backs up around the outlet, it can:

• Track underneath the membrane
• Saturate insulation
• Cause internal leaks
• Lead to long-term roof failure

This is why anti-back-up protection is essential.

The ClassicBond Internal Drain is designed specifically to prevent water or vapour travelling back up between the drain and the inside of the pipe, protecting the roof build-up below.

This product is available in three sizes to suit standard UK pipework:

• 68mm – Fits standard domestic 68mm rainwater pipes
• 100mm – Fits standard 100mm pipes
• 110mm – Fits standard 110mm soil or drainage pipes

Choosing the correct size ensures a positive pressure fit inside the pipe and proper anti backup performance.

ClassicBond internal drains feature:

• A smooth square bonding flange for excellent adhesion to EPDM
• A long outlet stem that pushes deep into the pipe
• Multiple outward-facing compression ribs on the stem
• A pressure-fit seal inside the downpipe

When inserted correctly, the ribs compress against the pipe wall, forming a tight seal that eliminates water backing up into the roof system or insulation.

This listing is for the internal drain outlet only, supplied with a leaf guard.

It does NOT include:

• Uncured EPDM flashing
• EPDM primer

These items are required for correct installation and should be purchased separately.

Installation method is the same for all sizes:

1. Trim the flange to leave a 25–35mm bonding area
2. Mechanically fix the drain securely into the roof deck
3. Install EPDM membrane over the roof (do not apply deck adhesive to the flange)
4. Cut the membrane using the flange as a guide
5. Apply EPDM primer to the flange and surrounding membrane
6. Install 9″ uncured EPDM flashing tape with a minimum 60mm overlap
7. Cut the centre hole
8. Roll firmly to seal flashing to membrane and drain
9. Insert the leaf guard

This creates a watertight seal on the surface and inside the pipe.

Most internal drain failures aren’t caused by the membrane, or the outlet itself - they’re caused by poor outlet detailing.

Using an anti back-up internal drain with uncured EPDM flashing tape and primer correctly removes that risk. Once installed properly, water has only one place to go: down the pipe, not back into the roof.

It’s one of the most important details to get right on an EPDM roof.