One way to promote a plumbing business in your local area is through your citations. Your citations are the information found on all the websites (Yelp, Angies list etc...) that hold your information (name, address,phone number etc...) You need to make sure they are correct but also present.  The more citations are accurate and consistent, the better your SEO for your website and more possibilities that when someone is looking for a plumber you show up.