T-Piece with Reducing Centre Flange Rigid Ducting Part — Metal Branching Fitting for Unequal Duct Sizes
Best for: Growers building custom ventilation systems where ducting diameters don't match
Our thoughts
This solves a real problem — connecting different diameter ducting without buying a separate reducer. Galvanised steel, proper engineering, no faffing about. If your extraction system needs to branch from one size to another, this does it cleanly.
The T-Piece with Reducing Centre Flange is a rigid metal ducting fitting designed to branch your ventilation system whilst handling unequal duct diameters in a single component. Made from galvanised steel, it features two outer flanges of matching diameter and a centre flange of reduced size — letting you connect different sized ducting runs without the need for separate reducing collars.
It's a straightforward efficiency play. One fitting instead of two, less air turbulence, tighter system control. Good for growers who want their extraction sorted without overthinking it.
How it compares
This sits in the mid-tier of rigid ducting fittings, positioned between budget PVC alternatives and commercial HVAC systems.
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vs. Standard Equal T-Piece: Standard T-pieces require all three connections to be the same diameter. This reducing variant lets you mix sizes, saving you a separate reducer fitting and the assembly hassle that goes with it
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vs. PVC T-Pieces: Galvanised steel outperforms PVC for larger diameter applications and lasts longer under regular use. Steel also moves air more efficiently with less friction loss
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vs. Flexible Ducting Systems: Rigid metal delivers superior airflow efficiency and durability. Flexible is cheaper and easier to route, but rigid wins on performance every time
In plain terms: you're getting a proper metal fitting that handles a specific job (mixing duct sizes) that most standard fittings can't do without extra parts.
Usage guidance
System Design
Use this when your extraction fan, filter, or intake point doesn't match the diameter of your main ducting run. Two identical outer flanges connect to matching diameter ducts; the centre flange branches to a different size. It's that simple.
Installation
Connect to rigid ducting using female-to-female couplings (slightly larger diameter than the fitting, slides over both connections). Seal all joints with quality duct tape or mastic to prevent air leaks. A tight seal keeps your extraction efficient — loose joints waste energy and kill system performance.
Placement in Your System
Keep ducting runs as straight as possible. Every bend or turn costs you airflow. Position this T-piece where your diameter change needs to happen, not as a workaround further down the line.
Common Applications
Connecting a carbon filter to your main extraction duct when sizes differ. Branching intake air from a different sized source. Linking multiple rooms with varying duct diameters. Any situation where standard equal T-pieces leave you short.
Technical specifications
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Material: Galvanised steel construction
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Design: Reducing centre flange with two equal outer flanges and one reduced centre flange
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Connection Type: Male spigot flanges (requires female-to-female couplings for assembly)
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Available Sizes: Standard UK market diameters include 100mm, 125mm, 150mm, 160mm, 180mm, and 200mm (specific reducing configurations made to order)
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Installation Method: Female-to-female couplings fitted over spigot connections, sealed with duct tape or mastic
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Durability: Heavy-duty, reusable, suitable for multiple system configurations
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Ordering: Made-to-order with custom diameter specifications available
Who this is for
- Growers building custom extraction systems from scratch and need to integrate different duct diameters
- Anyone retrofitting or expanding an existing ventilation setup where duct sizes don't align
- Experienced growers who understand ducting principles and want to optimise airflow efficiency
- System builders looking to reduce component count and potential leak points
- Growers running larger grow rooms or multi-room setups where diameter mismatches are common
Particularly well suited to setups where you know your exact duct sizes upfront and want to eliminate the guesswork around connectors and reducers.
Our take
This is a proper bit of kit that handles a specific problem cleanly. Galvanised steel, straightforward engineering, does exactly what it should. If you're building a ventilation system and your duct sizes don't match, this saves you hassle and money compared to buying separate fittings.
Worth picking up whilst clearance stock lasts. Rigid metal ducting components like this are the backbone of efficient extraction — get the fittings right and the whole system breathes properly.
