dust collection runs laid in concrete- need help please

[Dave Burson]

Just moved, and my new shop (YAY) will be a detached garage. I am adding on an additional 20x24' slab to house most of my wood tools. After seeing in a couple wood mags the option to run the DC mainlines within the concrete, and completely eliminate the overhead abacus of runs/tubes, I am hooked. But I don't really know how exactly. I am meeting with concrete guy this weekend, so hoping to get more educated so I know what to present to him.ANY help suggestions is MUCH appreciated!
Hereis wht I have- a ONEIDA 3 HP DC (not home, and don't remember the model, bought in 2000), but it is the hugely heavy metal wall mounted cyclone over a 35 gal bucket. I know it has 7" inlet, and in my previous shop I had 7" on main run, then 6" along ceiling, to 5" drops along walls to each machine. NOW, I want to go straight down, I assume will use 7", but then run 6" PVC under concrete and then 6" risers to each tool? This is where I'm not clear, since the concrete slab is only 4-5 " thick, and has to be reinforced with heavy wire.
If someone has done this, or knows specifics, I would LOVE to hear from you!
The beauty of this installation is clean efficent and quiet DC. The big negative, it is NOT flexible. I can't move it after install, so need to get it right, both in design, and positioning. HELP

TIA
Dave

[Frank Pratt]

Trouble is, once the slab is poured your tool locations are 'cast in stone'. I don't know anyone who's shop layout doesn't change from time to time. I have mine run overhead & honestly, it causes me no grief at all. I suppose if I had a basement I'd run the ducts under the floor.

[Jim Becker]

I agree with Frank. I'm not opposed to in-floor shop utilities, but I personally would prefer them to be adjustable over time. With a concrete floor, I'd probably opt for channels with removable covers so I could change out things like duct work, circuits, air lines, etc., over time and as new and/or different tools come into play. The alternative would be a raised floor or better yet, a crawl space over the concrete with a wood floor for the shop. My shop has been transformed multiple times since I set it up originally in 2000 and I'm about to make a few more changes to adapt to my current work flow requirements.

[Bill Dufour]

Need more info about your location. Where in the world do you live? does it freeze or rain a lot where water might cause issues. Earhtquakes or hurricanes or both? Do they inspect buildings there or can you do anything you want? Soil type, etc. etc.
I think you will have to dig trenches deeper then the main slab where the pipes run. probably need steel and rebar in the slab. this may weaken the slabs stiffness. if the soil is poor this can be a problem. If it freezes in your area you may have to dig deep anyway

[Jim Andrew]

If I were building a new shop, would pour a stem wall, and build the floor from lumber. Then, if you wanted to run your dust system under the floor, you would have a crawl space, and could hang the piping under the floor joists, and it would be possible to change your system if you get a new piece of equipment. I have my system hanging from the ceiling, and have changed things a couple of times. Main thing is, build your walls tall enough so you have room overhead.

[Charles Lent]

Pipes run under the floor will be cooler than the shop during the warmer humid months and moisture in the air will condense on the inside of the pipes, causing saw dust to stick. The only successful under floor runs that I know of were run through a concrete walled trench with a metal floor level cover over it. This provided an air gap between the pipe and the cool ground, preventing condensation in the pipe. Electrical conduit that is run under ground always needs the condensation blown out of it before the power cables can be run through it for the same reason.

Charley

[Lyndon Klassen]

The only successful under floor runs that I know of were run through a concrete walled trench with a metal floor level cover over it.
Charley

Well I'm going to double your current absolute-ness of experience because my dust pipes run under the floor and I have no problems.

[Bill Dufour]

Well I'm going to double your current absolute-ness of experience because my dust pipes run under the floor and I have no problems.

Maybe he lives in a desert so moisture is no problem. Is he the guy from Zimbabwe?
Bil lD.

[Jim Tobias]

My dust collection equipment sounds almost identical to Op and mine is run under a wooden floor with a crawl space. I have no issues at all with condensation. But I have radiant floor heating which may be the difference. The dust collection ductwork and the radiant hot water tubing both are just beneath the floor. I can't tell you how nice it is to have heat with no air movement. Just heat.
Don't know the location you're talking about but I would definitely consider this combo.

Jim

[Neil Gaskin]

I’d recommend min schedule 40 pvc. In a trench below the slab. Trench filled with hand compacted gravel.

[William Hodge]

In my experience, a dust collection system is temporary. The machines, projects, space, and equipment are always changing.

I worked in a shop that had some pipes under the wooden floor. We realized that 12" x 16' wood could fit in the rip saw if we moved the jointer 4''. Time for the sawzall.

Why would you want to make it so you couldn't move anything? It would be like playing volleyball with your feet velcroed to the floor. Perhaps entertaining to watch, but difficult to do.

[sean meltvedt]

Doug, Neil has it right. Treat it just like plumbing under the slab. My system is mostly under slab. I didn’t have all my equipment, nor a good layout when the concrete was going in. Instead I opted to put up risers to areas where I have clustered machines then plumb to each from the riser. It has worked so far with several reconfigurations. No issues with condensation in Alaska with the pipes below the slab insulation, radiant heat as well.
Enjoy your new shop space!
cheers
Sean

[ray grundhoefer]

The biggest problem I see with dust collection under the floor would be if you get water in it ,yes the sawdust might stick but worse would be the possibility of mold growing in there if it's always wet

[Frank Walker]

Put mine under the slab 32 years back with no regrets. 4" and 6" sewer pipe in the dirt under the concrete. Spot the main machines out in the open and single lines against the walls to branch up, left and right. Don't forget the electrical boxes.

Two table saws, two radial arm saws, two band saws, planer, joiner, lathe, sander, mortising machine, chop saw, and main work bench/ floor sweep. A few adjustments/ additions over the years but always worked out something. Pneumatic blast gate at each machine.

Frank

[andy bessette]

Trouble is, once the slab is poured your tool locations are 'cast in stone'. I don't know anyone who's shop layout doesn't change from time to time...

+1. Can't imagine putting it in a slab.