Even if one argued it is covered by 110.26(E), 110.26(E)(1)(b) provides for an exception for the hazard to exist provided the installation protects against the hazard. If the "weatherproof" nature of the installation is sufficient to protect against the result from a burst/leak of the pipe, I would argue you're good. I believe the exception also allows for the installation of a drip shield (specifically designed to protect the installation from the hazard) too, as it's being installed to protect from the hazard which seems to be the primary reason for the exception. Not to mention it makes sense. If your installation protects the device from the hazard...it should be OK.