Dust Collector Exhaust\Outlet Port Size

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Forum topic by lansinwd posted 12-16-2015 08:32 PM 788 views 0 times favorited 3 replies Add to Favorites Watch
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19 posts in 2362 days

12-16-2015 08:32 PM

Topic tags/keywords: question dust collection

I have an old Grizzly G1029 collector that I use with a 6” inlet (part available from Grizzly) and 6” main trunk pipe. I know that the exhaust\outlet port is actually only 5”, so I had been looking at increasing this as well. Speaking with a rep at Grizzly, even their brand new G1029Z2 still uses the same 5” exhaust port. This got me to wondering how important the size of the port really is. It would seem that it should be the same size as the inlet, but I haven’t been able to find any posts where people talk about modifying the exhaust\outlet port size, just the inlet (if it was not already 6”).

Is it worth the effort to change this, or does all of the concern about air velocity and CFM stop at the inlet?


-- Broken promises don't upset me. I just think, why did they believe me

3 replies so far

View Fred Hargis's profile

Fred Hargis

5309 posts in 2764 days

#1 posted 12-16-2015 10:29 PM

Last question first: no, it doesn’t stop at the inlet. A clogged filter can reduce air flow very effectively. One thing folks who vent outside should check is the motor amp draw to make sure the decreased resistance at the discharge end doesn’t allow the motor to overload. But I’ve not seen anyone try to increase the size of the outlet port. Anything I could think of would be speculation, but I suspect it’s not quite as simple as making the port bigger, it has some relationship (I would think) to the overall blower design.

-- Our village hasn't lost it's idiot, he was elected to congress.

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3280 posts in 1752 days

#2 posted 12-16-2015 11:03 PM

They’ve designed the blowers to function at specified CFM’s.
As Fred alluded to, I think there has to be a certain amount of outflow resistance.

I don’t think increasing the outlet by 1” will matter much since the vast majority of performance degradation occurs in the ducting system.

My collector has a 6” inlet and 4” outlet and works fine (vented to outside/no filters).

-- Everything is a prototype thats why its one of a kind!!

View conifur's profile


955 posts in 1423 days

#3 posted 12-16-2015 11:03 PM

Not an expert on this but by reducing the outlet it should increase the velocity, like putting you thumb over a garden hose.

-- Knowledge and experience equals Wisdom, Michael Frankowski

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