John Stevenson Plumbing, Heating & Air Conditioning in Carlsbad has held CSLB license #588895 with C-36 plumbing, C-20 HVAC, and C-34 pipeline classifications since its founding in January 1990. NATE-certified and EPA-certified technicians handle furnace replacements, ductless mini-split installations, and thermostat upgrades from the Loker Avenue West headquarters near Poinsettia Park — a combined plumbing-HVAC model also practiced by Coastal Refrigeration Heating and Air Conditioning, Inc. in the same North County market. The C-34 pipeline classification — uncommon among residential contractors — qualifies the company for underground sewer main and water service line replacements that most C-36-only plumbers cannot legally perform in California. Kitchen and bathroom remodels requiring gas line rerouting, supply-line stub-outs, and drain rough-ins represent a core project category, a scope that regularly intersects with general contractors including TNT Design & Build on permitted renovation work. Ten-year warranties cover all new HVAC equipment installations, and seven-year warranties apply to full ductwork replacements — both backed by the company's continuous Carlsbad operation since 1990. The highest-demand service tier includes hydronic radiant floor heating system design and installation, requiring calculated BTU load mapping, PEX tubing layout at 9-inch to 12-inch on-center spacing, and dedicated boiler integration.