How is a rain collar installed?
After the correctly sized collar has been selected; you will apply a 100% exterior or marine rated silicone caulk to the top of the existing rain collar attached to the roof flashing, and also to the underside of the new rain collar. Slide the new rain collar down over the pipe to the top of the existing collar. Press the new collar down with enough pressure to seal the two together without collapsing the seal around the pipe.