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EPDM Roofing

Drain Outlets - Technical Data Bulletin

Top Drain Outlets

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Top Drain Outlet


DuoPly TOP Drain outlet is one of the best means of connecting to an outlet drain. Its dimensions conform to UNI EN 1451-1, and it fits to bell and spigot jointed pipes without using adhesive. 

TOP drain flat roof outlets are particularly suited for use in low pitch roofs, under roof gardens, inverted roof systems and tiled roof areas. Fixing and fastening to the DuoPly membrane is by a threaded ring which allows for a compression seal when used with DuoPly Water Cut Off Mastic.

Features & Benefits

  • Quick and easy installation
  • Large countersunk top makes for easy flow of rainwater
  • Available in 110mm and 160mm diameter pipes.
  • 110mm - 492 lt/min capacity
  • 160mm - 786 lt/min capacity


1. Before laying the DuoPly membrane install the drain securely into the roof deck ensuring a sound connection into the rainwater pipe and a smooth flow from the decking into the outlet. Position the protective cover into the top of the drain opening.

2. Lay the DuoPly membrane over the outlet ensuring field seams are not running through the outlet. Press the DuoPly membrane down onto the protective cover to locate the central pin, cut the membrane so it protudes and using the cutting guide cut the circular section of the membrane out.

3. Once the circular piece of membrane and protective cover are removed. Apply a bead of Water Cut Off Mastic on the underside edge of the membrane around the circular hole, so that it will be clamped between the membrane and the body of the outlet.

4. Position the threaded seal ring onto the outlets and screw down into position, using the lugs, until fully tight. Finally clip the leaf grate into position with the three securing tabs.

Angled Wall Drain

Angled Wall Drain


DuoPly Angled Wall Drain primary use is to be installed as an outlet through parapet walls and small pitched roofs around the perimeter of flat roofs. The unit is made of a synthetic rubber that can withstand dramatic temperature change, high impact and is easily cut to length.

Features & Benefits

  • Large outlet opening of 90mm x 90mm
  • Outlet 500mm long with 1 metre extensions available
  • Accessories of leaf/gravel guard and 90 degree shoe
  • Used in conjunction with DuoPly Primer and
  • Uncured Elastoform Flashing tape.
  • Fast, economical outlet to install
  • Prefabricated manufacture.


1. Before laying the DuoPly membrane install the drain securely through the wall and fix into the roof deck and the upstand. Ensure the outlet is cut to required length. Preferably the outlet flange will be counter sunk into the decking.

2. Lay the DuoPly membrane over the outlet ensuring field seams are not running through the outlet.

3. Cut the membrane 50mm around the outlet hole, peel the membrane back and apply bonding adhesive to the rear of membrane and the face of the outlet.

4. Once DuoPly membrane is bonded, apply DuoPly primer to the EPDM membrane face and the exposed outlet and 50mm into the outlet pipe.

5. Once primer has cured apply section of DuoPly uncured elastoform flashing tape, cut a 15mm square out from the centre of the tape and work into the outlet opening.

6. Insert a secondary collar of Elastoform flashing into the pipe opening to reinforce the first section of elastoform tape applied to the outlet.


1. Ensure the outlet is free of all dust, moisture and contaminants before the DuoPly Primer is applied.

2. Ensure the outlet is firmly fixed into the upstand and into the decking.

3. Install leaf grate into outlet opening

Anti Back Up Drain

Anti Back Up Drain


DuoPly Anti Back Up flat roof outlet is a simple, effective method of connecting the flat roof system to existing or new internal 68mm rain water pipes. The prefabricated outlet unit has a circular seal built onto the pipe that creates a joint between the outlet and the pipe to ensure if the drainage system gets blocked the water can not back up inbetween the pipe and outlet into the joist space or under the roofing membrane.

Features & Benefits

  • Smooth flange for adhering the DuoPly Uncured Flashing tape
  • 185mm long outlet pipe with anti back up flange
  • High resistance to UV light, building movement, cracking and extreme temperature change


1. Before laying of the DuoPly EPDM membrane, the anti back up outlet must be fitted to the roof deck and securly inserted into the rainwater pipe.

2. Cut the top flange on the outlet back to leave 50-75mm of the smooth top around the outlet
opening. Securly fix this into the roof decking surface.

3. Adhere the DuoPly membrane onto the flat roof surface and over the top of the outlet. Do not apply decking adhesive to the top of the outlet.

4. Cut the membrane around the outside of the outlet flange so the membrane is sitting flush to the outer edge of the outlet flange.

5. Apply DuoPly Primer to the exposed top surface of the outlet and 50-75mm onto the membrane surface. Allow the primer to dry.

6. Install a piece of DuoPly Elastoform Flashing onto the primed area to join the EPDM membrane to the roof outlet. Next cut the centre of the flashing piece out to open up the outlet hole.

7. Finally roll the flashing tape with a 50mm hand roller and install the leaf grate into the outlet.


Ensure the outlet is the correct size for the rain water pipe. This is designed for the UK standard 68mm pipe size.

2. Make sure the outlet is securley fastened to the deck and correctly inserted into the rain water pipe .

3. Before application of the DuoPly Primer ensure the outlet and area of membrane to be primed is free of all dirt, moisture and contaminants.

Download the DuoPly Brochure

Registered in England and Wales, Company Number: 03984573

Registered Office: Flex-R Ltd, Sandswood House, Hillbottom Road, Sands Industrial Estate, High Wycombe, Buckinghamshire, HP12 4HJ

Telephone: 0800 037 1240   Email: enq@duoply.co.uk