# which 6" elbow for dust collector piping



## mickeyh (Oct 21, 2012)

Should I use two 45 degree elbows for a 90 degree turn or one long sweep 90 degree elbow? Has anyone experience with both and notice any different? I looked up SMACNA (fitting pressure drop charts) and the difference is negligible.

Thanks,
Mickey


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## FirehouseWoodworking (Jun 9, 2009)

IMHO, long sweep 90 is the way to go. The fewer the joints, the less chance of something getting snagged inside the ductwork. Good luck.

Cheers!


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## wapakfred (Jul 29, 2011)

The reason most folks advocate the 2-45's is that long sweeps aren't that easy to find. But if you can get them, that would be preferable. Your comment about pressure drop is interesting. I had a cyber buddy with measuring equipment, and he said in measuring the difference between a regular 90º el and the 2-45º els he also observed only a minor difference. I guess if you have several 90's in a run it can add up, though.


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## danoaz (Jun 16, 2012)

Not a fluid dynamics engineer here, but I wonder if the confusion comes from water association. Water in a pipe turning 90 degrees can create the "bang" you hear from the pressure causing a sudden drop at first but not so much with air because it is a gas and not a liquid. Being a light liquid as apposed to a heavy liquid like propane, it can turn corners more easily. Class dismissed.


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## mickeyh (Oct 21, 2012)

Here's what I found on SMACNA. The pressure drop for a 45 degree elbow is 0.6 that of a 90 degree elbow. Since we need two 45s for every one 90, the pressure drop is 1.2 times that of a 90. I guess I'll be using 90 elbows instead. A little more expensive but hopefully will be worth it.










If anyone is interested, the site for 6" fittings is www.midlandhardware.com under sewer and drain fittings. It's the cheapest place I can find.


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## mickeyh (Oct 21, 2012)

Here's a better image of the SMACNA table:


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## KMTSilvitech (Feb 10, 2011)

Great charts mickeyh


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