Reducers

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Duct Reducers & Duct Size Adapters for Grow Room Ventilation Duct reducers (also called duct size adapters or reducing couplings) transition between two different diameter duct sections in a ventilation system - connecting a larger-diameter fan port to a smaller-diameter duct run, or stepping down duct size between a main trunk duct and branch distribution ducts. In grow room ventilation, reducers are most commonly needed when a fan and a carbon filter have different port diameters, when a tent duct port does not match the fan's rated diameter, or when the available duct diameter does not match the intended fan size due to equipment from different manufacturers in the same system. Using Reducers Correctly A reducer introduces additional static pressure resistance into the duct system - the cross-sectional area reduction creates a restriction that the fan must work against, reducing delivered CFM. To minimize this penalty: use the largest available duct diameter for as much of the system as possible and only reduce at the final connection points where the equipment port requires it; avoid reducing by more than one standard size (6-inch to 4-inch is acceptable; 8-inch to 4-inch compounds restriction significantly). When possible, select fan and filter combinations that use the same port diameter to avoid needing reducers entirely. Browse our complete ventilation collection with inline fans , flexible ducting , and duct flanges . Expandable vs. Fixed Reducers Fixed metal reducers provide a rigid, low-resistance transition between two specific duct sizes. Expandable (flexible) reducers use a short section of flex duct with different-diameter cuffs at each end - they allow some angular misalignment between connected components but add more flow resistance than rigid reducers due to the flex duct material. For permanent installations, use rigid metal reducers; for temporary or adjustable setups, flexible reducers provide more positional flexibility. Fast shipping. Rel