dust collection runs laid in concrete- need help please

[Dave Burson]

Bill
Thanks for reply! I live in Fairfax, VA so it definitely gets cold, but not brutal cold like up north.
They do require building inspection, but not crazy inspections like some areas I've heard of. I will need to check on this though before I start for sure.

[Dave Burson]

Thanks for the input Jim! That is exactly what I'm toiling about, the ability to have them subfloor and out of the way which I would love, but the inflexibility that provides could be problematic for sure. The main issue to me is the run in the middle to my TS. What you mention with having channels with removable covers might be a great alternative that offers both. Hmmm... would have to think about how that could be done- ideas anyone??

BTW, I didn't mention, this is an addition to a standing 3 car detached garage, I am adding on 20', which would be part of the main shop area. It adjoins existing concrete, and I would put all my dust makers in that portion, so option going with wood where it is isn't really an option.

[Dave Burson]

Lindon
Could elaborate on where you live, and how you ran yours underground? I appreciate any info you can provide!!!

[Dave Burson]

Just moved from TX, to VA, but sometimes, leaving that many friends behind feels like being in Zimbabwe
Not in the desert for sure, although I do love AZ.

Not sure how the pipes here would handle the few deep freezes we get. Would definitely use schedule 40 PVC, probably 6" for the runs thru the slab. I love Jim's input about channels with removable covers, so I can lay out various positioning, and opt for some flexibility, just not sure how to do that.
Still not set in stone to the idea (pun intended, but want to explore all options before I start construction

[Dave Burson]

Have you seen this trench type installation Charles, or know anyone I could contact that has done it?
TIA!!

[Jack Frederick]

If you run the channels Jim suggests it will be pricey and you will be walking across diamond plate. I think the hot set-up would be the crawl space and wooden floor. Better to walk/work on and you have flexibility for the future. If you choose to go under slab you will glue each joint. Sch. 40 would probably be best. 6"can be a bear to make up. Fab up the main and then set it in the hole. Ream the inside edge of all cut pipe. Grade the pipe 1/4"/ft to an end drain. I doubt that you would have much of a moisture problem but build it to accommodate any that does occur. If you have an eccentric fitting at the bottom end you can see how the system performs moisture wise. I'd probably drill a small hole on the bottom and put a dowel in it. I would run this as a "Thru pipe system" with a clean-out on both ends. That way if you do end up with caked saw dust you can easily access the system. Pick your fittings carefully. Long radius, minimal pressure drop. No tees. 45 branches or Tee-Y's.
Every piece of equipment I have is mobile except my jointer and I am solving that issue this week, once it stops raining, by buying Martin's 8" jointer. You folks who can actually lay this stuff out and not change it scare me.

[Frank Walker]

If you decide on the below slab option, might want to consider a clean out arrangement at the DC turn up. Little blocks typically from the RAS will travel through my system but there is not enough velocity to lift them out at the end of the run ( my system is a 1HP drop box arrangement). My drop box is so large I only clean the shavings a couple of times a year (dust bags maybe once a month). I have three vertical pipes in the end of the drop box and just un plug the short pipe sections and reach down to retrieve any little pieces that might be sitting there.

For those that can't imagine a fixed underfloor system, I can't imagine all those overhead vertical drop lines in my way as I move materials around my shop.

Frank Walker

[Andrew Seemann]

I never would have gotten in-floor ducts in the right place if they had been an option for my current shop (the slab was in place when we bought the house). Even though I drew out the configuration of machine locations dozens of times and moved cardboard cutouts on the layout drawing in every conceivable place, I still ended up moving things the shop around, and still do from time to time. Some places where I thought a machine would work perfectly ended up being poor locations, and I ended up with some machines in places I never thought I would put them. What works on paper doesn't always work well day to day in 3 dimensions.

[George Yetka]

PVC is cheap if your sure of your layout throw it in and you can always plug it and run overhead later.

[Tom Bender]

To give yourself a little flexibility install drops into the floor in some extra places and just cap them. Set a female end flush just above flush with the floor prior to pouring. Trim flush and install some kind of a plug.

A little condensation (unlikely) will evaporate in minutes when you start the fan.

You are going to get sticker shock when you add up the cost of fittings

To make a cleanup in a riser just install a 12" long piece of pipe a few inches above the floor with Ferno couplings. Cheap and great access. And you can cut in a new one anytime.

[Patrick Maloney]

PVC is cheap if your sure of your layout throw it in and you can always plug it and run overhead later.

I ran my DC pipes (6" pvc...sch40 I think) under the slab, despite everyone telling me not to. I used grid paper and scale cutouts to plan for several different floorplans. I found that no matter how I arranged everything, the DC ports always ended up in roughly the same locations. I figured (like George said) I could always plug them and go from the top if things really didn't work out. So far I've moved some machinery around, but it was mainly swapping between the fixed port locations. The main machines that are out in the middle (tablesaws, shapers, planer & jointer) seem to be fine where I originally planned.

As for moisture, I've seen some occasionally, but nothing that makes me regret doing it like this. It causes some dust to build up a bit in areas, but I can easily disassemble any of the ports and sweep it with a chimney brush if needed. FYI....I'm in Ohio so it gets cold. I do have a deep gravel bed though (most of the pipe is in gravel rather than soil) but I'm not sure how much of a difference that makes. The slab is also insulated and heated, which is well worth the time and expense.

I also ran conduit for electrical to all the different clusters of machines. All in all, I would do it the same way again, except I'd put it more conduit and pull boxes everywhere...it's cheap and super convenient once you get insulation, drywall, etc... up.

Good luck!

[Charles Lent]

Have you seen this trench type installation Charles, or know anyone I could contact that has done it?
TIA!!

The friend who did this installation in his shop died 20 years ago. I don't think the new owner is a woodworker or even knows why he has metal covers over trenches in his garage floor. Sorry, I can't be of much help, but ask some electricians who bury conduit in concrete or direct ground contact if they have problems with water in the conduits. Any location where there is a difference in air pressure between the two ends of a buried conduit will have hot moist air flowing through it. When the air cools as it flows underground it will leave condensed humidity behind. Julie Moriarity is a retired electrician and member her. She once referred to "water in the underground conduits" in one of her posts here. I can remember this because I too was an electrician many years ago and I too had to blow out underground conduits before installing the cabling. Sometimes it's just a little, sometimes a lot. It depends on how cold the ground is and how moist the air flowing through it is.

I wouldn't expect pipes under a wood floor to have moisture problems like this, and insulated pipes or pipes with an air gap around them like those in a concrete open topped trench with a cover to have problems either. It's the cold ground in direct contact with the pipes that can have this problem.

Charley