While not necessary, it is a good idea.  The static generated during the manufacturing process can leave small harmless particles in the tank that should be rinsed out.  We recommend rinsing the tank prior to putting on the spigots.  Any residual particles that are not flushed during the rinse will float to the top when filling and can then be removed. Some customers will pour one or two cups of unscented bleach on the inside walls of the tank and then rinse for added peace of mind.