Home > Companies > Fixfast Ltd > FarBo® DuoDrain Flat Roof Outlets for Sealing to the VCL

Rainwater outlet consisting of two parts; the lower outlet connects to the vapour control layer (VCL) to create an effective seal at this crucial interface. The upper outlet is a standard FloDrain which is fitted through the insulation and into the lower outlet, creating a watertight connection.

Features and benefits:

  • Both outlet sections have a durable stainless steel spigot.
  • Membrane is easily attached to the upper outlet with either heat or solvent welding - providing easy installation.
  • Lower outlet is available in plain flange or styrene-butadiene-styrene (SBS) - compatible with most types of VCL.
  • Suitable for use in new build or refurbishment applications.
  • A variety of leaf guards are available for the upper outlet.
  • Manufactured in accordance with ISO 9001 and ISO 14001 Quality and Management Systems.


Rainwater outlets for use where a sealed interface is required at VCL level as well as roof level.

Standard product features

Spigot height:

  • Upper outlet: 400 mm.
  • Lower outlet: 280 mm.

Spigot material:

Stainless steel.

NBS Specification

NBS Create logo
This product is associated with the following NBS Create clause:
90-10-20/302 Gravity rainwater outlets

NBS Specification

NBS Buliding logo
This product is associated with the following NBS clauses:

Product specification

An important note about specifying



Fixfast Ltd


+44 (0)1732 882387

Product reference

Dark grey PVC membrane attachment, 350 x 350 mm.
Light grey PVC membrane attachment, 350 x 350 mm.
Bituminous membrane attachment, 500 x 500 mm.

Outlet diameter

[75 mm]
To suit 82–95 mm pipe size.
[110 mm]
To suit 120–128 mm pipe size.
[125 mm]
To suit 135–143 mm pipe size.
[160 mm]
To suit 170–178 mm pipe size.

Lower outlet

[Plain flange]

Leaf guards

For upper outlet. Consult manufacturer and insert requirements.
[Not required]

Manufacturer details

Merlin House,
Seven Mile Lane,
Borough Green,
Kent, TN15 8QY
Tel +44 (0)1732 882387
Fax +44 (0)1732 885532
NBS Plus