Female Connector Sleeve (Internal Coupling for Metal Ducts)

This is the sleeve for joining two rigid duct parts. It closes around the outside of both, so the run continues without a step. Galvanised steel, 100 to 250 mm.

A joint you cannot clamp

On flexible ducting you secure a joint with a worm clamp. Between two rigid parts that does not work: a clamp around stiff steel pinches nothing shut, it only slips.

So this connection holds by fit and overlap rather than clamping force. Push each duct part at least a couple of centimetres into the sleeve, so the parts meet over a real length.

Sealing comes afterwards, and it is a separate step that often gets forgotten. Aluminium tape around the seam is the quickest; two or three self-tapping screws through the overlap is the strongest, especially where the duct pulls on something. Preferably do both: the screws hold it in place, the tape makes it airtight.

A leaking seam costs more than you would think. Air drawn in there is air that never came from your room, so your extraction does work with nothing to show for it.

Available sizes

Technical Specifications:

• Coupling type: female, closes around the outside
• Joins: two rigid duct parts or fittings
• Material: galvanised steel
• Sealing: aluminium tape, optionally with self-tapping screws

Frequently asked questions

Can I put flexible ducting on it?
You can; the ducting then goes around the outside and is held by a clamp. For ducting onto ducting the male version is handier.

How much overlap do I need?
A couple of centimetres each side is enough. More overlap is stiffer and seals sooner.

Which tape works here?
Aluminium tape. Ordinary cloth tape lets go after a few warm months.