Dust collection duct question

[mark mcconachie]

(Go ahead, say the subject line three times real fast...)

Probably a silly thought, but is it possible to build DC duct work out of plywood and plexiglass? I know a/c ductwork is not the same, but boxed ducts are common in those systems. Picture three sides 3/8 plywood and the fourth plexiglass attached with screws to facilitate cleanout etc.

Ok, go ahead and let me have it... stupid idea? :D

[Erik Christensen]

IMO it would be a LOT more work and lot more expense than light wight pvc (I can get 10' of 6" pvc for $11 - don't think you could build it for the same cost) and depending on your DC prone to collapse if you shut off all gates - my 5 HP clearvue buckled the top of the trash can chip collector during initial testing before I beefed it up with 3/4" plywood

but hey - its a free country & you can do whatever you want - if you would enjoy making plywood/plexiglass duct-work more than cutting PVC have at it - let us know how it works

[Dan Friedrichs]

Yeah, people have done that, but as Erik said, it's probably not cost- or time- effective. I bet the plexiglass alone would cost more than PVC or metal pipe.

[mark mcconachie]

I am having such a tough time finding 6" PVC in the Portland Or area is why I was looking at doing this.

Any ideas?

[Eric DeSilva]

I am having such a tough time finding 6" PVC in the Portland Or area is why I was looking at doing this.

Any ideas?

I had similar issues. I ended up placing an order with US Plastics. Prices were quite reasonable, but the pipe came motor freight, which raised the price not insubstantially. Don't know if you have Menard's, but people seem to be able to get 6" ASTM 2729 there. I know my local big box stores--HD & Lowes--don't carry it. Another suggestion that didn't work for me but may work for you was checking with landscaping companies.

[Ray Newman]

I would look in the Yellow pages under "pipe" and "plumbing supply". Call a few and explain your need. If they don't carry it, they may know of a business that does....

[Fred Belknap]

The pipe is pretty reasonable when you can find it, it's the fittings that will break the bank.:eek:

[Erik Christensen]

even living in a pretty big metro area it took a while to track down 2729 pipe - finally found it at a place that caters to commercial landscapers - a LOT lighter & cheaper than S&D pipe

only gotcha with 6" pvc is the fittings - they only make them in SCHED80 so they are expensive - think a sanitary Y was 50$ and 45 deg 25$ (takes 2 to make a 90 but much better than a single 90) - I bet fittings was 80%+ of the cost of my duct work total

[Jesse Wilson]

Use DWV PVC I have found that it is the cheapest available in the 6" diameter.


Jesse

[Bob Abbott]

Mark, I recently bought 6" S&D pvc 2729 in the Portland area from Consolidated Supply Co. in Tigard. 10' sections cost $15.80. For connectors I ordered from Genova Products. 6" Wye was $17.74 and 6" 45 deg elbows were $8.51 each. I think there is a US Pipe also in Tigard that should have 6".

[Dan Friedrichs]

I am having such a tough time finding 6" PVC in the Portland Or area is why I was looking at doing this.

Any ideas?


Mark,

There's a Horizon Irrigation near you that should stock 6" ASTM2729 (sewer and drain) PVC.

8250 SW Hunziker Rd.
Tigard, Oregon 97223

They also have reasonable prices on fittings. They'll try to charge you the retail rate, but if you ask, they'll sell it cheaper.

If those fittings are too pricey for you, Ace Hardware Outlet carries them, and shipping isn't unreasonable.

[Chris Damm]

even living in a pretty big metro area it took a while to track down 2729 pipe - finally found it at a place that caters to commercial landscapers - a LOT lighter & cheaper than S&D pipe

only gotcha with 6" pvc is the fittings - they only make them in SCHED80 so they are expensive - think a sanitary Y was 50$ and 45 deg 25$ (takes 2 to make a 90 but much better than a single 90) - I bet fittings was 80%+ of the cost of my duct work total

If you get the proper fittings (ones marked for 2729 pipe) the prices are reasonable. I paid about $15 for my 6" wyes and $6 for my 45° ells.

[Steve Peterson]

They mention potentially building square boxes out of melamine to keep the resistance low. Plexiglass would be a nice feature when combined with a Clearvue cyclone. You could follow the dust all the way from the tool through the cyclone. I plan to build a closet for the cyclone so much of the "cool" factor would get lost.

I briefly considered this same thing after I started pricing PVC pipe and fittings. I forgot about it after considering the huge amount of labor involved. Every twist and bend in the line would probably take an hour or two.

I found 6" SDR35 pipe at a local plumbing supply house for under $3 per foot. Not a great price, but tolerable. I ordered fittings from http://www.acehardwareoutlet.com 45 degree elbows were $8.69 and Ys were $14.49. Shipping added around 20% on top of this.

Post pictures if you do decide to do the wood ducts.

Steve

[Alan Schaffter]

The main reason you don't want to use square or rectangular duct with a DC is because the internal resistance, that reduces CFM, is much higher per given cross-section. Also dust can collect in the corners.

The inside circumference of a 6" diameter pipe is 18.85".
Each side of a square duct with the same cross-section as the 6" pipe (28.27 sq. in) is 5.32" for a total of 21.28"

For the same cross sectional area (to pass the same CFM) the perimeter of a square duct is 2.43" greater than the circumference of an equivalent pipe (21.28 - 18.85). Multiply that difference by the length of the run and you can see how much greater the resistance will be in a square duct.

[mark mcconachie]

Well, I guess I know where I am hanging out from now on! Thanks for all the great input guys. I kind of figured the 'build your own' duct was not the right way to go, but with some sound reasoning, I have put that idea out of mind for good now.

Thanks to Dan and Bob, as well everyone else for the direction as to where I can find the 6" pipe in the Portland area. That was the original cause for my thinking about building it myself.

I am well on the way to spending some stashed cash and getting my DC system up and running... :)

Mark

[Eric DeSilva]

BTW, having just done this... I highly recommend the 6" blast gates from Clear Vue. I built my own floor sweeps and retrofitted some machines to put on 6" outlets--the CV blast gates made it easy, because you can just cut a large hole, and then screw the gate to a wood backer through the existing screw holes used to hold the thing together. They also just feel a lot nicer than the black plastic ABS gates I used for my 4" piping once upon a time...

[Greg Portland]

Mark, I bought my S&D pipe @ Horizon Irrigation when I used PVC. You can build rectangular duct out of plywood or MDF but it is not as efficient as pipes with a cylindrical cross section.

As you may have figured out, plumbing stores rarely carry 6"+ pipe. Irrigation suppliers are the best place to look.

[Alan Schaffter]

Comparison of PVC pipe:

Sched 40:
Home DWV pipe available at Borg (both 6" & 4")
Largest OD
Thickest wall
Heaviest
Pipe slightly more expensive
Fittings WAY more expensive

SDR 35
Available at most Borg in 4" some carry it in 6"
Is often green or blue color
Also called sewer & drain (S&D) and ASTM D3034
Thinner wall than Sched 40
Thicker wall than ASTM D2729
Same OD as ASTM D2729
Lighter than Sched 40, heavier than ASTM D2729
Uses ASTM 3034, 3035, etc. fittings (same as ASTM D2729, BUT NOT SCHED 40)

ASTM 2729: This is the one you want
Also called sewer & drain, S&D, "Solid Perf", Thin wall PVC, etc. (one style is perforated)
Only available in 4" at Borg
You can find 6" at irrigation suppliers and John Deere Landscapes (coast-coast locations)*
Thinner wall than Sched 40 and SDR 35
Same OD as SDR 35 (uses same fittings)
Lighter than both Sched 40 and SDR 35
Cheaper than Sched 40 and SDR 35

* Unless you are a farmer, landscaper, or are in the building trades JD will attempt to charge you double!

[Jim O'Dell]

Along with Ace hardware on line, McMaster-Carr online has 45 els, and 6-6-6-wyes. fVery fair shipping pricing, even though you don't get to see what that is when ordering. I ended up getting my 6-6-4 wyes and 22.5 els at Lowes, but not all of their stores carry it. I did find my pipe locally. The first 2 sticks were 1.86/ft. The last 3 were at 1.11/ft. It helps to find a big pipe yard and go look. Don't ask for S&D 2729. They don't have any clue what that is. Ask for 6" thin wall gravity fed drain pipe. The irrigation places here didn't have it, but I have 2 yards that have it now. Horizon listed above is one of them, but they weren't as friendly as the yard down town. Jim.

[mreza Salav]

I used spiral 6" galvanized ducting (instead of PVC). NO need to worry about static electricity. Wasn't that expensive either.

[Alan Schaffter]

I hope no one is worrying about static. I know Rockler, Woodcraft, and other vendors who sell grounding kits want the uninformed to worry.

[David Prince]

Not specifically mentioned, but shouldn't be ruled out. 6" metal duct pipe. When you install the pipe, caulk the long joints when you snap them together and use foil tape on the connections. 6" metal duct pipe is easy to find, not too expensive, and not too hard to work with. Downsize to 4" at the tool and 4" blast gates are easy to come by.