5-Minute Tech Quiz: What's New With the NEC?
Answer to: What’s Wrong With This?
Weatherproof boxes for outdoor use have an integrated gasket to seal the box from impinging water. Fittings used for connecting conduit (of any type) are rated for outdoor use as well. Using silicone or any other type of sealing material is not approved. See Article 314 of the 2014 edition of the National Electrical Code for more information.