Dust collection test: 90 degree elbow vs 45s

[Cliff Holmes]

I got to do some testing in the shop with my new DC. I've always heard that a pair of 45 degree elbows will work as well as a 90 degree wide-radius elbow. Well, my tests bear this out. I tested a WR elbow vs two 45s joined back-to-back vs two 45s joined with 12" of duct between them. What I found was that the back-to-back performed almost as well as the WR and the spaced 45s did slightly better than the WR. The difference between them, however, was very miniscule, only about 10 CFM between each one.

Just FYI, this is in 6" S&D with about 8' lead-in to the joint and 10' from the joint to the test point.

Considering that a WR elbow costs about twice as much as a pair of 45s, I'm heading back to Lowes to get some more 45s.

[Prashun Patel]

Thanks for those results. I'm curious how they compare to a regular 90 deg El.

[Cliff Holmes]

Me too, I'm gonna pick one up at Lowes and try it out.

[glenn bradley]

Two 45's offer a different sort of "swivel" if you have to snake around anything as well. I noticed this as a side benefit while figuring out my paths.

[Tom Veatch]

Glad to hear it, Cliff.

I used back to back 45's for all my 90° bends. My main reason was practicality. I knew (or thought I knew) I didn't want the short radius 90's and my local supplier (a plumbing supply wholesaler) gave me a "deer in the headlights" look when the subject of long radius bends came up. (Ducting is 6" ASTM 2979 S&D)