Torn PVC fabric loses its ability to hold pressure or to keep rain and wind from entering a protected area. One way to patch damaged PVC fabric is to heat weld the pieces together. Incorrectly welding the material can burn the edges of the tear, weakening the fabric or botching the repair so that the PVC pulls apart again soon afterwards.
Lay the plywood on a stable work surface. Place the PVC-coated fabric on the plywood.
Sand a 5 cm (2 inch) wide path along the edges of the tear in the fabric with 180-grit sandpaper until no clear coating remains. Do the same with the patch. Wipe off the sanded surfaces.
Mix the cleaner and water in the bucket until they are well blended. Soak the sponge in the solution and use it to clean the sanded sections of fabric. Allow the solution to remain on both pieces for 30 to 45 seconds. Rinse the fabric with clean water and let it dry for three to four hours.
Slide the adaptor on to the welder. Turn on the welder. Adjust its setting to 204 degrees C (400F) and wait until it reaches that temperature.
Set the patch, sanded side down, over the sanded tear. Slide the nozzle between the two pieces of fabric. Let the welder sit until smoke rises from the seam. Slide the welder one nozzle-width down the lapped seam. Immediately compress the heated section of the seam with the roller.
Continue working down the seam with the welder and roller until the patch is welded over the tear. Let the welded seam cool for 30 minutes before moving the fabric.
Move the welder more quickly if the edges of the fabric start to turn brown.