Light-gauge galvanized duct and furnace components: 26-gauge snap-lock pipe, reducers and increasers, 90° furnace elbows, fresh air vents, aluminum flexible ducting and square drain pans.
Snap-lock pipe ships flat and is formed into a round section on site by pressing the seam together, which is why it takes so little space to stock and transport. It is fitted crimped-end downstream, in the direction of airflow, so that any condensate runs inside the joint rather than dripping out of it.
Gauge is thickness, and the number runs backwards — 26-gauge is thinner than 24. Residential duct is typically 26 or 28 gauge; anything carrying structural load or spanning a long unsupported run needs heavier material.
Drain pans go under a water heater or an air handler to catch a slow leak and route it to a drain. A pan with no drain connection only delays the damage, so pipe the outlet where code requires it.
Galvanized duct is for air, not for gas or water piping. For threaded galvanized fittings, see Galvanized Iron Fittings.
