There are over 701,000 LinkedIn profiles related to HVAC and Plumbing in the US. Here are a few things that can help you stand out:
Professional and/or family photos
Completed profile —- this will take some time as well, but very worth the effort :)
Explain your goal for LinkedIn profile - for example, open to new job opportunities, connecting with industry professionals, etc
Explain your short and long term career aspirations
Full job title and responsibilities
Add employer’s LinkedIn. Company page as your company
Certifications, licenses, training
Referrals - give and ask for referrals. Note, a great way to receive referrals is to first write recommendations about your LinkedIn connections.
Important - keep everything positive, not offensive on your profile.
Post meaningful content that your connections will find interesting on occasion - create your own content (start a blog), paste interesting news articles, share things periodically that are funny as well, share company, projects, and/or industry events or achievements.