Under-slab DC - for those who have done it

[Tom Godley]

I am still deciding on what is the best way to proceed with my shop floor -- but I keep coming back to the DC piping and if I should put some of it under the floor.

I have no idea of the placement of the tools. I am always changing something - so I am not going to place any outlets in the middle of the floor area. But I was thinking about maybe running a pipe from one corner (I think the best place for the DC) out to the farthest two walls. Most of my tools end up along the walls anyway. This way I would not have to hang it from my ceiling which is more of a barn roof with the sides sloping to a high (14') flat ceiling in the middle.

Anyone go this route? Pipe recommendations?

[Ken Garlock]

Hello Tom.
I when I had my shop built as part of the home building project, I had the concrete/slab contractor put a 7" deep by 7" wide trench down the center of the 25X25 foot shop. The trench carries 6" PVC pipe and collects dust from my planer, table saw, router table, and jointer. Each tool has a 45 deg elbow that makes the connection to the main 6" line. A couple blast gates are standard metal, and two are my own design, a disk that rotates 90 deg to open/close off the specific tool.

To cover the trench I had a local steel supplier cut me some 1/8" diamond plate in the lengths I needed. The trench was made to have a 1/8 wide and 1/8 recessed lip for the steel to set in thus giving a smooth surface between the concrete floor and the steel plate.

My dust collector was built from a kit that WAS available a couple years ago. It is an implementation of the Bill Pentz design. It is located in the corner of the shop. The PVC pipe runs along the ceiling and against the wall. The supply for the major tools is a vertical PVC pipe that connects the ceiling main to the pipe in the floor trench. The ceiling pipe then continues to the far corner and along the ceiling, parallel to the trench, with 45 deg drops to the band saw and miter saw. I did not pipe the other two walls since one contains full length built-in tool cabinets. The other has a double door and the electric panel. Speaking of electrical, the trench also carries a 240v, 30amp 10 Ga. line to feed the tools along the trench.

Good luck with your project.:)

[tyler mckee]

I have never done it but i like Kens idea, I would try to somewhat plan where my machines will go and locate a trench or two to catch everything. I wouldn't want everything enclosed in concrete as then you are stuck with what you have unless you want to spend some time with a jackhammer or have pipes snaking across the floor. the ability to throw in electrical and air lines would be a big plus too.

[Tom Godley]

Ken - I remember seeing this someplace -- maybe you posted it.

It does sound like a good idea. I ultimately would like to cover the shop area with a wood floor -- plus I live in a radon area so all of that trench would have to be formed on the bottom -- not just cut out.

[Josh Bowman]

I have a 30 something by 40 something shop. I put power outlets at each of 4-four inch dust collector risers. I used thin wall pvc that is just below the slap. To keep it from floating up I used giant staples made from rebar. Some of the bends are a little tight. You might work that out better with more 45's. The result is a very efficient system. I have had no problems with moisture. Consider 6" pipe, but 4" is fine for my 2 hp grizz. I have one outlet that gets swapped from the jointer to the planer with a quick disconnet. 1 is dedicated to the PM 66 table saw. 2 have not been used.
My regrets are that I did not add an underground collector port from my radial arm saw.
When the concrete pour took place, I marked the pipe runs so the concrete folks would not step on the thin wall shallow pipes. I had no problems, but if I had used thicker stuff that would not be a problem. But since I have stuff that mates to the thin wall I used it.

The outlets were ran with 3/4" conduit so I could change from 110 to 220 as happened when I upgraded my table saw. I bought some uni strut from HD or Lowes and took 2 or 3 foot pieces and staked it into the ground. I then used a thickwall metal elbow to get below grade, then went to PVC to the box location. I guess I'm hinting to use underground outlets. They have been wonderful. If you are willing to spring for the bucks, you can buy flush mounted outlets that machines can roll over. Since my budget on my shop doubled, I tended to cut back some.
Hope this helps some.
Josh

[John McClanahan]

A trench sounds like a good idea. Be sure to include some sort of a drain, just in case.....

John

[Tom Godley]

If I was sure of the tool placement - having them perfectly set up would be great. But this is not the case -- and it forces you to keep the tool in that location. Plus, having it a little off is sometimes worse than not having it.

My thought was to simply run a couple of lines out to the far walls of the shop -- this would allow me the luxury of not having a big trunk line crossing my open ceiling. I would then work somewhat backwards to the tools - the lines may be a few feet longer but I work alone so only one tool would be in use.

[Josh Bowman]

If I was sure of the tool placement - having them perfectly set up would be great. But this is not the case -- and it forces you to keep the tool in that location. Plus, having it a little off is sometimes worse than not having it.

My thought was to simply run a couple of lines out to the far walls of the shop -- this would allow me the luxury of not having a big trunk line crossing my open ceiling. I would then work somewhat backwards to the tools - the lines may be a few feet longer but I work alone so only one tool would be in use.
I'm not sure of your shop size, but a piece of graph paper and some squares and rectangles of you stuff will help you alot. Also make a couple of rectangles that represent a 10 or 12 foot board as well as a 4x8 ply to ensure the machines will function in thier spots. You don't have to be that close really. Short runs of flex will correct most problems. Bottom line is most shops don't move certain items, like the TS and Radial arm saw or any other large equipment. So those you make right, the other stuff, put them on wheels and share a common floor outlet. That's how I do my jointer and 15" planer. My point is the DC will work much better if the dust and chips are falling, not being pulled up. Most of all the big trunks of hose is out of the way and PVC is cheap.

[Chris Parks]

If the ducting will not be accessible then allow for clear outs in the system and plan how you would clear a blockage if it did happen. Easiest way most probably is to have the ends of the ducts actually in the side face of the slab with screw caps on it. To do this I would lay ducts the length of the slab and branch off these as required. With access to each end clearing a blockage would be easy as long as it is in the long runs as it most likely would be.

[Terry Hatfield]

Condensation in the ducts could be an issue with it in the slab and being locked into tool placement is not something that I personally would like. I would vote for overhead and not in the slab. The ducts in the slab sounds like a good idea but it is my opinion that the drawbacks outweight the advantages.

t

[Josh Bowman]

If the ducting will not be accessible then allow for clear outs in the system and plan how you would clear a blockage if it did happen. Easiest way most probably is to have the ends of the ducts actually in the side face of the slab with screw caps on it. To do this I would lay ducts the length of the slab and branch off these as required. With access to each end clearing a blockage would be easy as long as it is in the long runs as it most likely would be.
My 4" system is far from perfect, I have had lots of blockages, but none ever in the slick pipe under the slab:D. Most to all happen at the DC's inlet chunk stopper:o.
I'm trying to get brave enough to remove it, but soon as I do, off goes a piece of 2x4:(
If you run under slab the runs are very short since they run directly back to the DC from the machine. If you run overhead as in my previous shop, it has to go up out of the way, follow some route that is out of the way and then down. Now with an overhead system, my planer blocked almost 6 feet of 4" pipe. As I said above, I have had the DC block up at it's screen and the pipe then filled with stuff from my planer, but when the DC was cleared, it sucked all pipe clean. Here how I looked at it. I put an under slab in with cheap PVC and it might have cost me 50 buck. If I didn't like it, I was going to saw the inlets off at the floor and put plugs in it. They then be used to run wire for an outlet. However my DC performace really improved. If I had not been so cheap, the system would had been even better.