Hose-end fittings into flex ducting

[Vince Shriver]

Does anyone know the trick of fitting 4" flanged hose-ends into spiral flex ducting? Maybe soften the end of the duct in boiling water or with a heat gun?

[George Makra]

Try a 4 inch no hub connector.
Its in the plumbing section and looks like a large hose clamp with a rubber sleeve inside.
It will allow you to tighten on to different diameters with in reason.

[Jim Dwight]

I am using 5 inch metal in my current shop but my last one was 4 inch S&D PVC. I'm working from memory but I believe I got a nice tight fit of flex into the female end of the 4 inch PVC - the end where the other pipe can slide in.

If you need to, PVC can be expanded or shrunk with a heat gun. The Oneida super dust deputy can be too.

[John Lifer]

I used a 4inch HDPE pipe for my collector runs. The fittings from grizzly and others fit ok, but pipe was easily shrunk with heat gun to be tight fit. I did use a single wrap of duct tape to really make things airtight (inside) and if I thought it needed it, a quick wrap of aluminum ducting tape.

[Tom M King]

These are probably sold somewhere else too, but I remember seeing them here:
https://classicgutters.com/product-category/downspout-expanders/