# 2.5" vs. 4" Dust collection hose...



## PKFF (Dec 16, 2011)

Right now, I have a shopVac with the vortex dust seperator as my dust collection system. I need to hook it up to my Grizzly Table saw but it has a 4" port. Right now I have a reducer at the port to bring the port size down to 2.5 inch. My question is, if I were to reduce it earlier, say at the dust collector (i.e. run a 4 inch hose from the saw to the vortex seperator and reduce it there,) do you think I would gain any suction. I know my shopVac is severely outmatched when it comes to dust collection, but it is merely temporary as I just upgraded from a contractor table saw.

I'd rather not upgrade the dust collection at this time as I had just upgraded the saw…one tool at a time!


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## Loren (May 30, 2008)

I've run a 4 inch hose to a separator trash can lid and out with
a 2.5" hose to a dumpy Craftsman 6 gallon shop vac and the
setup pulled a pretty acceptable amount of chips from a couple
of different planers I used it on.

Try to keep the 4" line as short as possible, I'd say.


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## pmayer (Jan 3, 2010)

That is a good question. I have never thought of it because generally you want to start big and reduce as you need to, and you are going in reverse. I believe you will be better off running the 2.5" all the way to the tool and having the adapter at the tool, but keep the hose as short as possible. This should at least keep your air velocity higher closer to the tool. Either way your air volume is going to be painfully low for a table saw with 2.5" hose, but I know you already know that. My shop vac with 2.5" hose moves about 80 CFM, and you need at least 400 at the table saw to even remove most of the bigger debris, and ideally you would be in the 800-1000 CFM range to remove fine dust.


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## Lifesaver2000 (Nov 17, 2009)

I have been using a shop vac and pre-separator (trash can and Thien baffle) for a couple of years. I just completed building my second one about a month ago, this one is a "top hat" design, and I used four inch ports so I could upgrade at some point and still use it. Right now I run 2.5 inch hose from the vac to the separator, then from the separator to the tools (table saw, miter saw, router table and planer) one at a time.

My next upgrade, as soon as I can pick some up, is to change the hose between the separator and the shop vac to four inch. This latest separator works so well that in the process of producing about 30 or 40 gallons so far of sawdust, there is NO visible dust in the shop vac or in the shop vac HEPA filter. Since there is nothing but air between the separator and the vac, upgrading this to four inch should reduce friction loss without causing any problems.

I plan to continue to use the 2.5 inch hose from the separator to the tool, because I am concerned the shop vac might not move the air fast enough in a larger hose to keep the saw dust in suspension.


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## McFrisch (Jun 24, 2020)

What happens when you go the other way? I just got upgraded my Rigid shop vac/Dust Deputy (2") to a Shop Fox W1685 with 6" or 2×4" ports. My miter saw connected well to the Cyclone, using a fernco reducer and 2.5" flex line. I wonder what will happen if I reduce the 4" flex from the dust collector to a 2.5" at the tool.


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## pottz (Sep 15, 2015)

shop vac's are all about suction dust collectors are all about moving a large volume of air,it's not gonna work well but for temp it's better than nothing.just think of it as having a bad head cold and it's hard to breath.


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## rwe2156 (May 7, 2014)

+1 on what pottz said.

You need CFM's for machines not velocity and suction.


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## Lazyman (Aug 8, 2014)

I would definitely keep the smaller diameter hose all the way to the saw. The higher velocity will help make sure that any dust that gets into the hose actually makes it to the vac instead of getting caught on any internal coils or joints. Depending upon the saw's innards, you may be able to improve things by adding some plywood or even cardboard baffles to funnel the sawdust towards the vacuum port.


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## clagwell (Dec 20, 2018)

> What happens when you go the other way? I just got upgraded my Rigid shop vac/Dust Deputy (2") to a Shop Fox W1685 with 6" or 2×4" ports. My miter saw connected well to the Cyclone, using a fernco reducer and 2.5" flex line. I wonder what will happen if I reduce the 4" flex from the dust collector to a 2.5" at the tool.
> 
> - McFrisch


I depends upon the size of the miter saw port. If it's say, 1", then you might get about 40 CFM. That's almost certainly less than what you get with the shopvac.

By the way, that's not a reduction from 4" to 2.5". Airflow goes FROM the tool TO the DC, so that's actually an EXPANSION from 2.5" to 4".

Also, you will probably get more answers to your question rather than to the OP's by starting a new thread instead of resurrecting one from nine years ago.


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