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Welzig Heating and Air is your proven, trusted, and expert source of plumbing installation in Boulder, CO and surrounding areas. Whether for replacement or starting from scratch, we focus on your priorities and requirements to achieve the best possible results. Simply give us a call at (720) 336-3777 to discuss your project and take advantage of knowledgeable information, insight, and modern innovation.

Need New Plumbing Fixtures?

From conventional and tankless water heaters to sump pumps, water filtration systems, plumbing fixtures, and more, Welzig Heating and Air is where you find exceptional quality and satisfaction guaranteed. Recognizing that any compromise in products, materials, or workmanship results in ongoing issues and expenses, we are meticulous about every detail and step of the job. If you’re interested in greater enjoyment, reliability, and longevity from your investment, we’re definitely the right choice.

Expert Plumbing Installation

Family-owned and operated, Welzig Heating and Air offers free estimates on equipment replacement and satisfaction guaranteed across Boulder, Longmont, Louisville, and Lafayette, CO. Ask us about our financing options with approved credit. Let us tell you about the latest developments in plumbing technology to elevate efficiency, comfort, convenience, and hygiene. We look forward to making exceptional improvements to the everyday needs of your home or light commercial facility.

Satisfied Customers
They Speak For Us

Dave Kaplan-Gomez and James Miltersen installed my new Tankless Water Heater. Both were polite and professional. Care was taken not to damage anything in my house which I really appreciated. I use Welzig for all my HVAC needs and highly recommend them.


Bob came out to look at our swamp cooler and was remarkably helpful and professional. Not only did he give me a knowledgeable diagnosis, but he also taught me a lot in the process. We’ll be calling him for all future needs with our cooling system.


Our 23-year-old A/C system ran out of “borrowed time” and became too difficult to continue maintaining. With great advice from Casey Welzig,, we replaced the old system with a Bryant Evolution A/C system. Max Loustaunau and Seth Bernhardt did an excellent job with removing the old system and installing the new one. Both of them are great to work with — very professional and very personable. We are really amazed at how much better the new system works!

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