# Dust collection pipes under concrete floor



## Anderjack (Mar 16, 2020)

First post- Hi Folks!

I'm planning a new 16'x 36' shop later this year in which I'll have the opportunity to run my dust collection lines (as well as electrical conduits and compressed air lines) in/below the new concrete slab floor. What recommendations / do's & don'ts / tips & tricks / general wisdom do you all have?

I'm looking for the things that worked out really well for you and the things that you might do differently.

Thanks!


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## woodnthings (Jan 24, 2009)

*I don't have any experience with under floor dust collection, but ...*

The "rules" are similar to overhead.
Avoid long runs.
Avoid 90 degree turns, using 2 - 45's elbows instead.
Use large enough pipe.
Since concrete contains lye, you may want to consider plastic drain pipe rather than galvanized. Make certain the slab stays dry at all times. Know where your water table is. Level the ground/dirt first, then apply 2" or more of dry sand. Then cover with Visqueen and more sand. Then pour your slab. My 5" house slab also has 2" of Styrofoam underneath it all and down the footings to isolate them from cold, here in Michigan. 

Blast gates will need to be above the slab, so make then easy to access or automatic types.
The pipe layout can be diagonal with the DC unit at the end or a closed circuit run:
https://www.google.com/search?q=dus...525&client=firefox-b-1-d#imgrc=4RycKZUos7hapM


https://www.pinterest.com/pin/6614730688584041/


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## woodshed (Feb 11, 2020)

How are you cleaning and finding parts in pipes? Sawdust can be collecting and hardening in pipes. What if important part is sucking and falling in there, like expensive arbor nut? Maybe including cleanout access in plans?


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## kiwi_outdoors (Jan 15, 2020)

bad idea to put any/all utilities if its not necessary. Overhead utilities can be rerouted and repaired and modified so very easily..


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## Anderjack (Mar 16, 2020)

Great suggestion- not that anything like that would ever happen to me, right? Thanks!


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## Anderjack (Mar 16, 2020)

Thanks - I appreciate and don't disagree with your comment. My main concern with this new shop is lack of space - I'm "putting 3 pounds of stuff in a 2-pound bag" so to speak, so I'l be going overhead and underground with whatever makes sense. Still - your comment gives me reason to pause and think more about where I might not want something like a piece of pipe or conduit stubbed up in the future.
Thanks!


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## JayArr (Sep 18, 2018)

Hi Anderjack


If you want to run things in the floor just make a channel instead of burying a tube. Conduits and vac lines will likely run mostly around the outside edges of the shop so you can cover the channel with a board (set in so it's level) and you won't likely walk on it, it'll be behind the equipment. I see this in factories all the time, they cover it in diamond plate but that's not necessary, a 2X6 will work.
You can have the advantage of underfloor routing without the permanence if buried conduit.
JayArr


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## GeorgeC (Jul 30, 2008)

I think that running your electric and compressed air in conduits under the concrete floor will be OK. I would use the piping as a conduit for the compressed air, not actually the compressed air pipe itself. You want to be able to remove and replace the actual wiring/piping if necessary.


I would not run the dust collection. As noted there are potential problems there.


George


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## ducbsa (Jul 6, 2014)

GeorgeC said:


> I think that running your electric and compressed air in conduits under the concrete floor will be OK. I would use the piping as a conduit for the compressed air, not actually the compressed air pipe itself. You want to be able to remove and replace the actual wiring/piping if necessary.
> 
> 
> I would not run the dust collection. As noted there are potential problems there.
> ...


Pulling lengths of pipe out of the conduit for replacement will require some planning before construction starts.


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## DrRobert (Apr 27, 2015)

Personally I would not run any utilities or air supplies under a slab the main reason being shop layouts change, work flows change, and new machines may be added at a future date. This is figured out after the shop is built and you actually start using it.

That said, I do have one section of duct under slab to my table saws to eliminate the obstruction of the drop down.


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## woodnthings (Jan 24, 2009)

*I like this idea ...*



JayArr said:


> Hi Anderjack
> If you want to run things in the floor just make a channel instead of burying a tube. Conduits and vac lines will likely run mostly around the outside edges of the shop so you can cover the channel with a board (set in so it's level) and you won't likely walk on it, it'll be behind the equipment. I see this in factories all the time, they cover it in diamond plate but that's not necessary, a 2X6 will work.
> You can have the advantage of underfloor routing without the permanence if buried conduit.
> JayArr



This idea will solve any access issues. A channel with a 2 X plank that rests either on a rabbett cast into the concrete OR 2X's placed in the channel at a lower height to support to planks resting on therm above.





DrRobert said:


> Personally I would not run any utilities or air supplies under a slab the main reason being shop layouts change, work flows change, and new machines may be added at a future date. This is figured out after the shop is built and you actually start using it.
> 
> That said, I do have one section of duct under slab to my table saws to eliminate the obstruction of the drop down.



The advantages are mostly of a "safety" issue from tripping hazards.
A 4" pipe can be a large floor obstruction, so most shops run the DC pipes overhead. That method has it's own issues..... conflicts with other overhead utilities like lighting, visually unappealing, gravity works to keep things at the bottom of the drops, vertical drops to machines that get in the way of swing long boards, but nothing too 
much to deal with, however. :|

My solution requires floor space for 2 Jet 1100's on mobile bases that get wheeled short distances to the machine being used at the time. I use short 4" flex hoses to reach the planers, jointer, drum sanders, and table saws. I use quick disconnect fittings to minimize change over times. The 3 joined table saws have a common 4" suction pipe underneath which terminates near one of the Jet 1100's for easy access. 

Running DC pipes under a slab is very labor intensive and would require a pretty well thought out floor plan..... subject to change in the future. My shop layout has gone through about 4 changes, getting new tools, removing older ones, etc. The only tool that has not moved is the ultra wide 3 table saw setup. I guess, if it were me, I wouldn't do it. 

:vs_cool:


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## electricianswoodshop (Jun 14, 2020)

This is new to me, so please forgive any noob mistakes.
I am in the same situation. I am about to build a shop. It will have a slab and I know the layout I want. I am considering putting the dust collection piping below the slab, pryer to pouring the concrete.
My worry is that the piping mat sweat, as I will be putting AC in the shop, as well as I live in lower Louisiana and humidity is unbelievable here. 
I am not worried about leann out. What I haven't found, anywhere on line, is, with the dust collector on, using a dryer vent clean out tool ($20 at Home Depot) for 4" and there are companies that make the same in 6" and 8' brushes. As well, it may be possible to use a flexible chimney sweep brush on a drill.
Also, any suggestions on a good dust collection unit, cheap but efficient?
Thanks for any help.


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## TomCT2 (May 16, 2014)

regardless of sweating/humidity/condensation/anythingelse.....


when putting piping under concrete, you need to consider some kind of holes/access points through the concrete so you can get to piping runs to clean out / brush out / suction out / rod out any jams. making a hole/cleanout port is so much easier when pouring concrete than having to cut a hole in hardened concrete.


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## woodnthings (Jan 24, 2009)

*Run some wire inside the ducts first*



electricianswoodshop said:


> This is new to me, so please forgive any noob mistakes.
> I am in the same situation. I am about to build a shop. It will have a slab and I know the layout I want. I am considering putting the dust collection piping below the slab, pryer to pouring the concrete.
> My worry is that the piping mat sweat, as I will be putting AC in the shop, as well as I live in lower Louisiana and humidity is unbelievable here.
> I am not worried about leann (clean?) out. What I haven't found, anywhere on line, is, with the dust collector on, using a dryer vent clean out tool ($20 at Home Depot) for 4" and there are companies that make the same in 6" and 8' brushes. As well, it may be possible to use a flexible chimney sweep brush on a drill.
> ...



I would run some 16 GA stranded wire inside all the ducts for pulling any brushes through the ducts. BUT remember to tie a "return wire" on the brush before you pull all the entire wire through. :| Just leave them inside the pipes, they won't hurt anything. Tie them off and run them through an 1/8" hole near the floor. 



THE most popular DC on the market is the 2 HP Harbor Freight model with a cloth bag, on sale with a coupon for under $200. typically about $140.00. You Tube has a million videos on mods for them. Some exhaust directly outside, no bags or filters. Others separate the motor and separator and hang the unit on the wall with a Wynn cannister filter. 



As for sizing the DC pipes, bigger is better than small. Bill Pentz has a web site that will tell you more than you want to know about dust collection:
http://billpentz.com/woodworking/cyclone/


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## CharleyL (Jan 13, 2019)

Pipes running in the ground will condense moisture out of the air flowing through them because the ground is cooler than the air. A friend gave up trying to use his dust collection pipe under his shop floor because the condensation kept collecting saw dust on the walls of the pipe, requiring considerable effort to clean it out frequently, and doing this cleaning was a significant chore requiring a vacuum, and chimney sweep brush on extension rods. When running electrical conduit underground, if the wires aren't pulled very soon after installation, I have found it frequently necessary to use compressed air to blow the condensation out of the conduit before pulling the wires. It's amazing how much moisture collects in them. If I ever build a new shop it will have trenches in the floor with diamond plate covers, and the dust collector pipes in them will be insulated with foam sleeves to avoid any chance of the cold concrete causing condensate build-up in my dust collection pipes. If there is ever a problem or need to modify the pipes, I want to be able to get to them as well. 

Charley


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## electricianswoodshop (Jun 14, 2020)

Thank you for your reply. I have to agree that there could be condensation in pipes underground. I will build the shop ceiling at least 9' high, so I think I should be ok putting a 8" pipe down the center of the shop, then branching off to tools on each side. As well as 2 drops in the middle of the room.


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## TomCT2 (May 16, 2014)

you'll want to do some homework on pipe sizing. an 8" dia pipe will require a lot of cfm to keep stuff suspended in the airstream for transport.


here's a randon exhaust - it sucks air from under the slab. one year I was late getting the dehumidifier going. 

there will be condensation under the slab.


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