We have not specifically tested how long Gorilla Tape will last when directly exposed to the sun before it starts to flake or degrade, but we do know it should withstand direct exposure to UV rays (such as in South Florida) for some months.  Gorilla Tape has a number of features that will help its UV resistance, but it does not specially contain any UV stabilizers.  The darker the tape, the better performance against UV, so due its color and thickness, Gorilla Tape will withstand UV rays better than most duct tapes. 

However, if the pipes are PVC, I would recommend using an acrylic tape for this application.

I hope this helps.

MaryEllen