You don't want to be one of the many sources that simply sell finish plumbing products. You want to be identified as a source for design, largest display of quality products, talented/knowledgeable sales consultants and the best service available.
Branding simply (well, maybe not all that simply) involves developing and consistently communicating a group of positive characteristics that consumers can identify with and relate to your business. If these characteristics happen to fill a meaningful and available position in their minds, a need they have been wanting and trying to fill, then you just scored a marketing home-run, and you'll be well on your way to meeting your sales and profit goals.