For my 16 gallon shop vac, I found the following components in the plumbing aisle:
- A length of two inch ABS pipe.
- Two inch sink trap to form the 180 degree bend for the gutter.
- A 2 1/2 inch to 1 1/2 inch rubber reducer
- Extra extension for the shop vac to provide the necessary extension length to reach the roof from ground level
The 2 1/2 inch reducer has a pipe clamp that easily attaches to the extension.