we used Gas Masters for a whole house gas repiping, including 3 HVAC systems, water heater and 3 gas fireplaces. We had a very good experience with them. they are licensed and I did verify their license in the state licensing board database. most HVAC contractors do gas piping, but it's an afterthought for them, whereas Gas Masters just focuses on gas piping. they recommended a manifold system design, which I had read was superior because it minimizes joints/connections, but other contractors had tried to steer me away from because it uses more materials. They use high quality materials, including the best brand of arc/lightning-resistant flex pipe and black pipe where appropriate. the same person, Zach, does the initial estimate/sales and also supervises the crew, this is rare as many other contractors send an impressive sales person but then nothing of what you discuss is incorporated into the quote or communicated to the crew. they were also able to squeeze us in quickly given our emergency situation with no gas no heat in the middle of winter, and also willing to quickly go back and forth with us on specs and incorporate all requested specs in writing into the contract. They coordinated the permitting and inspection and kept things moving until the gas was back on. Zach communicated with us frequently throughout the job on progress and answered all questions along the way. the technicians in our crew, Sergio and Justin, were competent, nice and respectful. They did not make a mess in our crawlspace or leave any kind of mess or debris behind. All of our gas lines are clearly labeled for easy identification going forward, and each line has dedicated cutoff valves and regulators. I would recommend Gas Masters for any gas work - whole house repiping, leak repair, gas fireplaces, pools, outdoor decor, etc.