Dust Collection Duct Layout Advice Needed

Alan in Little Washington

Alan Schaffter
Corporate Member
No line on engineering data, but in one respect it is logical. Two bends in sequence have an extra joint which adds to the resistance. I try to avoid 90's of any type whenever I can, where I can't I used long sweep ASTM 3034/SDR 35 which are a bit more expensive and harder to find and I don't recall the radius but it is much greater than a normal 90° elbow.

One solution which isn't applicable to all locations is to use a 45° wye and run the drop at 45° . Another option is to combine a 45° wye with a 45° bend to achieve a 90.

or use one of these with one branch blocked if needed:

 
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Rushton

Rush
Senior User
Thanks for providing more suggestions. I will run as much of this as I can with a 45-degree wye and the drop at 45. But I have several locations where I'd need a 45-degree wye and then a 45-degree bend to vertical. This is where a sweep 90 would reduce the number of joints in series, which might be advantageous if the sweep 90's loss coefficient is not worse.
 

Alan in Little Washington

Alan Schaffter
Corporate Member
I googled it, found a number of images some with sources, e.g. Menards (mid-west?)
I found a couple with with a bit less sweep from Grainger on this catalogue page: https://www.grainger.com/content/general-catalog?pagelabel=2810&search=20LU69

And this (pricey) SDR35/ASTM D3034 elbow from Southern Pipe & Supply They have a branch in Athens.



Thinking outside the box, Champion Fiberglass has long sweep fiberglass electrical conduit elbows (PVC adapters available) but I have no idea on cost .

The prices of this stuff have gone crazy over the years.

Have you actually sourced 8" SDR35/ASTM3034 (or 8" ASTM 2729)? I have never seen it nor fittings for it anywhere, just 8" Sched 40. If it is made and you can find and buy it, even though lighter than Sched 40, it would still weigh a ton and the pipe and fittings will cost and arm and a leg. You might consider running two 6" ASTM 2729 mains. Ooops, I looked again, it appears Ferguson sells 8" SDR35. But you also have the issue of getting 8" X 8" and 8" X 6" fittings (Check out Ferguson's price for 8" SDR fittings!), so I still would consider going with all 6"!

As far as the 6" ASTM 2729, it is still available. One readily available source used to be John Deere Landscapes but I believe they sold out some years ago. It Greenville it is now called SiteOne Landscape Supply. There appears to be a branch in Huntsville, AL. However, just like when it was John Deere, unless you have an account with them, are a contractor, or know a contractor who will buy it for you, you'll pay almost double, literally. The retail price shown for 6" bell end ASTM 2729 is $3.89 per ft.! I think I paid about $1.30 per ft many years ago. (since I used fittings in most places, I cut off the bell end plus 3 or so inches of pipe and used it for flex hose quick connect- with a little work you can stuff flex into the bell end of ASTM 2729)
 

Rushton

Rush
Senior User
Alan, thanks for continuing to stay in this! I appreciate your help.

What coincidences! The elbow you found is the one I also found late last night. It is manufactured by Normandy Products and it does seem to be built on a bit larger radius than what I've been seeing:

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I found it available for retail online sale from Drainage Solutions. at a lower price than Southern Pipe & Supply ($22 vs $32) and shipping costs from Drainage Solutions strike me as reasonable for the market today.

Yes, I did find the SDR 35 8" straight pipe and fittings locally at Ferguson Waterworks. They only have the gasketed pipe, but their price is not terribly bad at $57 per 14' stick (ouch!, but I only need 3), with free local delivery. Their sales guy searched for me to see if he could source any weld end pipe, but no luck. Nor did he have access to any D-2729 8" pipe. So, I'm planning to use the SDR 35 for my 8" pipe.

I haven't found a local source for 6" D-2729 pipe. I was able to find it in Richmond 3 years ago, but nothing in this region. However, McMaster-Carr does carry it in 10' sticks at $32 per stick (link here) and their shipping cost is not unreasonable. Plus, if I end up ordering some other items from McMaster, they'll try to fit it all on the same pallet to ship.

Yes, the 8" fittings are expensive, but the sales guy I talked with quoted me some better pricing than you're seeing on their online price list. Also, Drainage Solutions has it for less (e.g., $66 for the 8x8x6 45 wye vs. the price list of $113) and I think Ferguson may match those prices.

For the 6" D-2729, I think I paid about $25 per 10' stick in Richmond three years ago. I understand the price of materials has skyrocketed and availability is really down right now.

Thanks for the link to SiteOne! They do show the D-2729 in stock in Huntsville, and I may have someone who can buy it for me at contractor rates if they won't deal with me directly. I'll have to look into this. It would be great to be able to buy locally and not have to ship it.

You have a good suggestion for using the bell ends for connectors.
 
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Rushton

Rush
Senior User
Now that I've found the Normandy Products 6" 90-degree elbows (the ones with the larger radius curvature than others we see), I've completed our duct layout design and thought I'd share it here. I still have some work to finish on the separate 6" drops in the center of the floor for the bandsaw and table saw. In some instances where I've used 90-degree turns for the drops I could have made the connection with a 45-degree drop, but we need the wall space to build in some storage. So, some trade-offs are made in this respect.

Thanks for everyone's help thus far! Questions and comments welcome.

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Alan in Little Washington

Alan Schaffter
Corporate Member
Unless you have an unrestricted budget and really want to wrestle a lot of heavy 8" pipe, this is what I would do. Of course in reality if it were me, I would have run all 6," no 8"- big savings on pipe AND especially fittings. (see how many fittings and how much pipe of both sizes, I eliminated!) Remember, the goal is shortest, most direct route to DC with fewest fittings and bends, especially killer 90° bends. I would run the 6" line to the jointer from the main down the wall at 45°, and have the drop to the drill press come off at a 45° wye. That eliminates the second 45° to the drill press and results in a straight shot to the jointer blastgate eliminating the wye and 90° completely. I would do the same and share the drop to the lathe and bandsaw and also the drops to mitersaw and router. Somehow I got double images. Also, I focused on the mains and didn't bother redrawing the drops in the first overhead view. You can usually get the drops to lay flat against the wall by rotating the 45° wye and using one or two 22.5° bends.

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Rushton

Rush
Senior User
Thank you, Alan. Your suggestions are very good! This is what I love about getting different eyes on a project - you've seen things differently. I'll play with this to see if I can get all of our drops to work without that extra 8"trunk that you suggest deleting. Looks like this can work! And if it can work, it should be more efficient air flow.
 

mpeele

michael
User
If I were to guess, I'd say it was the higher SP (resistance or pressure drop) per foot of flex vs smooth wall duct. It is fairly significant- 3 times (According to Bill, "Even good smooth walled flex will increase resistance three or more times over straight duct.") but you guys can check for yourselves. I found it in two places on Bill's site- the quote above in the ducting section (3. Flex Hose & Hose Clamps ) and also on one of Bill's spreadsheets, but couldn't find it elsewhere in the text, but I didn't spend much time looking. I just discovered my name and a link to my autogate video unfortunately the link longer works and I didn't make into the acknowledgements page. :(
I've seen references quoting static pressure losses in wire reenforced hose of 3 to 5 times that of smooth steel pipe. It is always stated as straight and I've never seen a quote for loss through a bend.
 

Rushton

Rush
Senior User
So, for any who have been following along, here is the "final" design of the duct layout for our Clear Vue CVMAX installation - at least until it all changes. I've incorporated several recent suggestions, with great thanks to Alan in Little Washington and to everyone else who has offered comments. I'm moving on to ordering pipe and connectors based on what you see here. Most people will make their layouts using only 6" pipe, just as I did in my last home shop. But in shared use community shop, I have to plan for two machines being operated simultaneously by different users. This design will allow for any two machines NOT sharing a blue 6" branch to be operated simultaneously. This design criteria led to several of the choices of layout for this shop. For example, a bandsaw and the table saw could be used concurrently, or both bandsaws, but not the table saw and the planer.

Summary of changes: 90-degree bends have been eliminated to the wood lathe and to the jointer (per Alan's recommendation). The 8" trunk extension at the first wye has been deleted in favor of an 8-6 reducer to 6" pipe to the sanding station by itself. Two 90 degree elbows still remain in the system since replacing them with paired 45s does not improve resistance over these longer than typical sweep (nearly 1R) 90s. (Too bad we don't have true 2R and greater sweep 90s available in SRD35 connectors.) The branch line into the small work room on the left has been eliminated - all dust creating activities will have to occur in the main shop and we won't mix swarth from the metal lathe with wood dust in any event. Those two salmon colored post are floor to ceiling posts to accommodate bracing for the down drops and to bring 220v conduit down from the ceiling for the table saw and bandsaw.

Blast gates continue to be only at the 6" branch lines with no 4" blast gates. I may need to find a way to reduce some of the 4" lines to 3" when paired with a 6" pipe (that should ideally be reduced to 5"), such as at the miter saw station, but this will be fine-tuning at a later time.

Still to do: 1) more work on the Festool miter saw station layout (which will incorporate below the table dust collection as well as collection through the built in dust port), 2) the movable router table (currently shown in its "docked" location to the left of the miter saw), and 3) improved dust shroud designs for many of the machines, particularly the belt/disc/spindle sanders.

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Alan in Little Washington

Alan Schaffter
Corporate Member
Now, just remember what I said in one of my earlier posts about friction fit duct joints with maybe a small screw to hold parts together and sealed with just a tiny bit of pure silcone (no latex or hybrid caulk) applied to outside of each joint after assembly. Because, contrary to your description of it as the "final design," someday, likely sooner than later, you will need to pull sections of duct apart to reconfigure- to accommodate unforseen needs- change in work flow, new machine, etc., etc. ;)
 

Rushton

Rush
Senior User
Yes, we will do that! Friction fit, a bit of pure silicone, and a small screw if and where needed. :)
 

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