125mm Round PVC Ducting Pipe

Frequently asked questions

What is 125mm round ducting?

125mm round ducting is rigid PVC duct with a 125mm diameter, also called 5 inch ducting. In the Domus range it is called EasiPipe 125. It suits larger cooker hoods, inline extract fans, MVHR branch runs and longer domestic extract runs.

Is 125mm the same as 5 inch ducting?

Yes. 125mm is the metric size and 5 inch the imperial name for the same duct. Any fan, cooker hood or wall kit sold as 5 inch will fit 125mm ducting.

Rigid or flexible ducting?

Use rigid duct for the main run. It has lower resistance, makes air tight push fit joints and does not sag or collect grease and dust. Use flexible hose only for short final connections, ideally under 1m, pulled taut and clipped with a Jubilee clip.

How do I join 125mm duct?

Push the plain end of one length into the socket of the next, or use a straight connector to join two plain ends. Tape each joint with aluminium duct tape for an air tight seal, and support horizontal runs every 600 to 800mm so they do not sag.

Do I need to insulate the duct?

Yes, wherever the duct runs through a cold space such as an unheated loft. Warm moist air hitting a cold duct wall condenses inside and can drip back to the fan. Use Domus Thermal insulation shells on bends and wrap straight runs in duct insulation.

125mm round or 204 x 60mm flat?

They suit the same fans and cooker hoods. Use 125mm round where there is room, as it is cheaper and has the lowest resistance. Use 204 x 60mm flat duct where depth is tight, and join the two with a round to rectangular adaptor.

How long can a 125mm duct run be?

125mm has much lower resistance than 100mm, so it handles longer runs. Check the fan's datasheet for its maximum, and allow about 1.2m of equivalent length for each 90° bend and 0.6m for each 45° bend.