More about Duct
Types of Duct
The silver bullet is added to the end of the house fibre to make a smooth tiny pointed end to help guide it during blowing.
The house fibre duct is 2mm diameter including 2 glass fibres and other layers of coating.
The white 5mm duct is the duct that passes through the house wall.
The gas block seals the duct so that it cannot leak underground gas into the house. It lives in the grey connector box screwed to your outer house wall. That’s all the grey box does, it just hides this.
The black 7mm duct is the one that is okay in sunlight, the one that comes out of the ground and goes up your house wall.
The usual 7mm connector. To the right is the clip-on protective cover for this connector. To the left is a more recent connector that twists closed, it is less popular than the old sort.
The standard 7mm orange, also available in red.
You can just see a whitish duct that fits between the usual 16 and 7mm sizes. Hard to come by, but a useful size
The 16mm size for Core Fibre. Offcuts easy to come by.
Three standard sizes of outer duct that fit together. 25mm, 32mm and 40mm. The 15mm slides easily inside the 25mm so 25mm can be used as a protective layer. The other sizes fit snuggly, so a join can be made in the lower size by using the next size up as a collar.
Other Examples of Duct
A Some 25mm protective ducting attacked by a digger.
B This was one of the blockages that the 288f fibre came across. It was more squashed than this but has the ability to self-heal to some extent. Other samples from blockages have returned to nearly perfect.
C Chewing by cows. Loose ends left in a field for a week.
D You can’t easily see it, but this 7mm has longitudinal scratching from the moleplough, making the watertight-ness of the cap suspect.
E A piece of core fibre showing its 288 strands.
F A 72f and a 288f core fibre for comparison.
Samples from the only multi-core ducts used in Dentdale.
Seven-Core as used over Church Bridge containing 7X15mm ducts.
Five-Core as used in our first trench at Millbeck. The central white duct is just a spacer.
Twin core. Convenient for a long run to an isolated pair of houses. Tough to peel back the outer layer. It took 2 years to use this drum up.
Multi-core is very unwieldy.
Video from Emtelle showing how to cut multi-core duct. It can be done with a Stanley knife but use of the special tool that cuts to a specific depth is easier. B4RN have this tool, you could probably borrow it.