The drainage characteristics of the roof and any subsequent necessity for slopes to drain or additional drains must first be determined by the roof designer. The Sika Sarnafil roof membrane is installed over the insulation board (when applicable) and a round hole is cut into the Sika Sarnafil membrane directly over and equal to the existing drain pipe diameter.
Existing leader pipes shall be cleaned of excess bitumen build-up, dirt and debris.
Remove any clamping ring assembly and bolts from the existing drain, where present, and discard.
Inspect the existing water leader to ensure that there are no elbows or similar such obstructions that would prevent the Sarnadrain with U-Flow® drain stem from being fully inserted. (Where elbow or obstruction exists see guidance below as to how to shorten the stem).
Insert the U-Flow seal into the end of the drain stem and tighten the screws (using the U-Flow screwdriver) enough to secure the seal into position during installation.
Insert the assembled Sarnadrain into existing leader pipe (where present) until the flange lies flush onto the Sika Sarnafil membrane. Tighten the seal compression ring screws, again with U-Flow Screwdriver, until hand tight.
The Sarnadrain with U-Flow flange is fastened with Sarnafasteners into the roof deck, using a minimum of three fasteners evenly positioned around the flange. For roof decks requiring specialty fasteners, a wood nailer shall be installed and fastened first and the drain flange is then fastened into the wood blocking with 1-¼" (31 mm) Sarnafasteners. Sarnadrain with U-Flow is properly installed when no vertical movement results when pressure is placed on the drain unit.
A target panel / flashing of Sika Sarnafil membrane is then hot air welded to the drain flange and the surrounding roof membrane according to Sika Sarnafil’s detail drawing. Ensure that all membrane and flange surfaces are clean prior to welding.
Once welds have cooled, check with a rounded screwdriver blade.
Install the strainer dome onto the retaining clips and insert nylon push-in fasteners into the appropriate height hole in each of the three retaining clips.
HOW TO SHORTEN DRAIN
Ensure that there is at least 4" (100 mm) of clear vertical distance in the existing pipe to allow the drain to be fitted.
Cut the drain stem to the desired length and insert the U-Flow seal.
Note: A minimum of 2-½" (62.5 mm) of drain stem is required to house the seal.
Insert the U-Flow seal into the cut drain stem and tighten screw seals.
Insert fully assembled and seal-fitted drain into the existing water leader and complete the installation as detailed above.
