DC Pipe...PVC vs Metal?

[Jay Yoder]

I am in the throws of laying out (and constantly revising) my shop and dust collection arrangement. I have read and studied the "Woodshop Dust Control" and have determined (based on the tables in the book) that the largest diameter I need is 6" main runs with 4" branches. I am using a Jet DC1100 w/canister and will only use one machine at a time. the largest chip generator in my shop currently is my Dewalt DW735 planer, which may be replaced by a full size 15" type in the distant future. My questions are as follows...

1) why does the book recommend "slowing" the flow in the main ducts, wont it increase the liklihood of it settling out? The reason behind the question is when pricing PVC (DWV type) I saw about a 250%+ difference between the 4" and the 6" and associated fittings, I was shocked at the cost of 45's and 22.5's in 6"!! Not to mention 4" had a much better selection. All my equipment has 2 1/2" or 4 collection fittings...The galvanized cost difference was negligable, but fittings not nearly as accessable.

2) are there any advantages/disadvantages of PVC versus Galv snap loc pipe and fittings? For the galvanized, the book calls for 24-26 ga and not 30ga which is what is available at the box stores in the area. Any issues with going with 30 as long as blast gates are not all left closed? I would like to build a system with either material that could be reused if I upgrade to a cyclone in the future.

Thanks for looking and your input is greatly appreciated!

[Paul Demetropoulos]

Jay,

Two advantages of the pvc are that it's cheaper and quieter. The 6" fittings can get pricey but the metal spiral are as well, and the metal pipe is much more.

..and check out the thread "thoughts on dust collection..part 2" that's running, lot's of good stuff

[glenn bradley]

+1 what Paul said and the 6" fittings are a fraction of what the metal ones are. As an example;

a 6x6x6 wye in PVC at $16: http://www.acehardwareoutlet.com/(vk4bga45rkvlb0fudejuhu20)/productDetails.aspx?SKU=47994

and in metal at $40: http://store.oneida-air.com/6x6x645degwyejoint.aspx

or $95: http://www.grizzly.com/products/6-Industrial-Dust-Collection-Standard-Branch/G7353

[Tom Veatch]

...
1) why does the book recommend "slowing" the flow in the main ducts, wont it increase the liklihood of it settling out?
Power loss. The power loss (pressure drop) is a function of the cube of the velocity in the duct. To move the air twice as fast through a duct requires 8 times as much power. As long as you maintain an air velocity that sweeps the duct clean, anything faster is very costly in terms of power required.

[Chris Padilla]

Jay,

Two advantages of the pvc are that it's cheaper and quieter. The 6" fittings can get pricey but the metal spiral are as well, and the metal pipe is much more.

While I agree with the pricing of metal vs. PVC I'm not so sure that it is quieter. Things bang around the duct just as much. Besides, most of the noise is at the impeller housing (the DC) so it overshadows any noise reductions that might exist between PVC and metal.

Metal has more sizes...like odd: 5" and 7". These don't exist in PVC but no matter. If you go all 6", you should be in good shape with PVC. Metal DC fitting also "flow" in the correct direction unlike HVAC which "flows" the other way (HVAC blows...DC sucks...makes a difference in how the fittings connect to ensure air-tight, smooth connections).

Some may claim shock hazards and dust expolsion with PVC. Forget trying to "ground" your PVC--big waste of time and very difficult to do properly. Will you get shocked by PVC: yes. Will it blow up due to all the sawdust? Highly unlikely in a hobbyist venue. Over time, the ability for the PVC to shock will dissipate.

[John Keeton]

Two advantages of the pvc are that it's cheaper and quieter. The 6" fittings can get pricey but the metal spiral are as well, and the metal pipe is much more.
This is only true unless one uses HVAC ducting. A wye runs about $7, and you can have them made up in any configuration you want. The cost of my entire ducting system was about $400 as I recall. My shop is 24x24.

There are drawbacks, as you need to lay down the inside tabs and tape them prior to assembly, but I have no complaints on the efficiency of my system.

[Michael Peet]

I just installed metal ductwork for my new cyclone last fall. I was tempted to go with PVC just out of familiarity and availability, but in the end I decided on snap-lock (not spiral). I thought there might be a lot of difficulty trying to finagle PVC to fit on the DC and machinery.

The metal ducting was not difficult to install. The hardest part was getting the adjustable elbows right. The tricks are:

1. It's a two-person job
2. Wear heavy rubber gloves - you get a lot of grip and they will protect you from the sharp edges
3. Align the alternating segments of the elbow to get a bend in only one plane.

Oneida is a notoriously expensive place to get the metal ductwork, but I was pretty happy with it. I picked my DC up since they're nearby in Syracuse, so I saved on all the shipping.

[Jay Yoder]

Thanks for all the excellent info. I was not going to use the spiral, too expensive for my available budget....I would prefer to go the HVAC (snap loc) route b/c of weight. I already have the crimper so custom lengths are not an issue. Another advantage is the weight will be less and I can ground it easier. Is 30ga heavy enough? that is what the blue borg carries. I will plan on maintaining the 6" with 4" drop philosophy. Ultimately the winning material will be a blend of cost versus selection of fittings...

[Jim O'Dell]

I personally used PVC. From reading here and at other forums, the consensus is that 30 guage is too thin, especially for the higher powered systems, and double especially if you close all your gates. :eek: ( your original post doesn't designate what collector you are using. Sorry if I missed it along the way) 26 guage seems to be the thinnest that works well. Many say they can find local makers of spiral that comes out about as cheap as the PVC. I think you have to look just as hard to find that supplier as most of us experienced finding the thin walled PVC. Jim.

[Jay Yoder]

Jim,
I am using a Jet-1100 with canister filter. Where did you get your fittings? Did you have any trouble sourcing long radius elbows? or I guess the rough equivalent would be using 2 45 deg fittings together...I guess one solution to the 30ga dilemma with blast gates all closed would be to install a floor sweep that is always open...then again, i would prefer to just make sure a gate is always open...

[Paul Demetropoulos]

Jay,

I still think pvc is the better choice, the S&D is light ( don’t get the heavier schedule 40) and easy to hang, and easy to take apart as well; and I still maintain it's quieter. And if you’re going to use 6” mains with 4” drops as you said, regular blast gates fit right into the 4” S&D pipe, makes life much easier believe me.

If you decide to go with the metal pipe, I agree with what Jim O’Dell said that 30ga. is too light. You don't want to have to remember to leave a gate open and with the Jet 1000 which is 1.5 hp, an always open floor sweep may kill your flow. If you look around I think you’ll find that makers of DC equipment don’t even offer 30ga. HVAC type pipe as option, 26ga. being considered “economy” and 24ga. premium. Like the plastic the metal is easy to install.

[John Keeton]

Jay, do NOT use 30 gauge for straight runs. It is OK for elbows, etc, but see here (http://www.sawmillcreek.org/showthread.php?t=79131)for proof!

[Jim Becker]

I personally prefer metal duct due to the size availability. There are many situations where 5" is the "perfect" size to do the job, for example, and a number of cyclones, including my 2hp Oneida Commercial have 7" or 8" inlets that would be impossible to service directly with PVC. For snap-lock, you want 26 gage, not 30 gage. It's sometimes called "stove pipe" since that's its common use outside of the woodworking community. You will not reliably find it at the 'borg, although Home Depot does sometimes carry it in 24" pieces if you look carefully. (Silver or gray logo on the boxes) Don't discount spiral, however....many folks have found local sources for spiral pipe at about the same cost as snap-lock. Some fittings will cost more in metal for DC since you need to source them from folks who cater to DC, but a good design can help minimize and optimize these components. Be careful as some of the vendors have both "heavy duty" and "not heavy duty" components and the former cost a lot more than the latter...the latter is just fine for what most of us need. Kencraft is also a good source for laterals and long-radius adjustable elbows as well as straight snap lock. Most of my fittings did come from Oneida, however.

[Joel Earl]

Yesterday I was doing the local buddy shop tours and drooling at what they got. Not that I would use it but it's all so purrrrrrty:D

3 had cyclones ranging from a PSI Tempest that I think was 2.0hp up to a big G0441 that is 3hp. I know some of you have bigger and badder suckers but this was big league stuff to me.
Ducting was interesting - all used some form of 30ga metal for parts of the components and the PSI was all 30ga. I know thats light stuff and with that kind of power they have would have been mighty reluctant to do same. Having said that they all stated they researched and asked a lot of users who have done the same if they ever had issues. Nope. The only thing any have heard of was the comment and pics above on that section that collapsed awhile back. Each uses smaller sections of the 30ga stuff - 5' was longest single piece. Maybe that helps avoid stress? I dunno - they somehow got it all to work fine. I know Wood mags cyclone design from years back was 30ga too so ?????

This DC thing is a wee bit overwhelming isn't it:eek:

[John Keeton]

Joel, from my experience with the collapse of the 30 ga. I would say that having a 5' span of 5" would be much less likely to collapse than in my situation. The rigidity of the 5", I would think, would be considerably greater than 6". The run that collapsed on my system was 6", and about 12' between connectors. The elbows and wyes are very stiff at 30 ga. and I would not expect any risk of collapse at those points.

[Joel Earl]

Hi John - thanks for that info. I wasn't sure if longer meant weaker but it does seem in some way it may be so.
I may have screwed up if I stated 5" - it was 6" metal, 30ga and the sections were at that 5' length.

Regardless I still think it might make me nervous with a cyclone being that light and I'd prefer something heavier. I'm lazy and hate to do things twice:D

[John Keeton]

Joel, I am sorry - must have misread your post. You did not mention 5". My duct was also in 5' sections, but the collapse occurred in a run that had about 2.5 sections between an elbow and wye. I think longer does mean weaker as I still have a short section (about 3') of 30 ga. left in my system. It does not flex at all, so I left it after the collapse. Doing it again from the outset, I would not consider using 30 ga. at all, except for the fittings.

[Sonny Edmonds]

LMAO!
30 gauge?
My Woodsucker is 16 gauge. Real steel.
And a closed wheel blower. Louder, but far more powerful.
Let the buyer beware.

I think Oneida is the best one going right now.

Be careful of off shore stuff made of pie pans. ;)

[Paul Demetropoulos]

3 had cyclones ranging from a PSI Tempest that I think was 2.0hp up to a big G0441 that is 3hp. Ducting was interesting - all used some form of 30ga metal for parts of the components and the PSI was all 30ga. I know thats light stuff and with that kind of power they have would have been mighty reluctant to do same. Having said that they all stated they researched and asked a lot of users who have done the same if they ever had issues. Nope. The only thing any have heard of was the comment and pics above on that section that collapsed awhile back. Each uses smaller sections of the 30ga stuff - 5' was longest single piece. Maybe that helps avoid stress? I dunno - they somehow got it all to work fine. I know Wood mags cyclone design from years back was 30ga too so ?????This DC thing is a wee bit overwhelming isn't it:eek:

When you say the "PSI was all 30ga." you're saying that's what your friend hooked up to it, not that it's a system that came that way from PSI; I don't think that's clear, it wouldn't. Go on their site, the lightest guage ducting they sell is 26ga., this could be misleading to Jay who asked the original question.

Jay, why don't you call the Oneida people and get a recommendation from them, you know, go to the source.

[Joel Earl]

In reviewing what I posted I suppose one could maybe get confused. I was indeed talking about ducting only.

As far as the old Wood magazine homemade cyclone - that was a PSI DC that they used to power it and that too was made from 30ga.-to clarify this, the cyclone body was 30ga.

Hope this now is clear and sorry if anyone missed my meaning.

[Eric Gustafson]

I may have screwed up if I stated 5" - it was 6" metal, 30ga and the sections were at that 5' length.

I am using pvc with my cyclone, but I saw where someone re-enforced 30 ga metal ducting on long runs to prevent the tube from colapsing. They use a plywood ring that fits the OD of the metal duct.

[paul dyar]

My first system was 4" pvc. I moved my shop and wanted to go up in size, so I went to metal. I have the Grizzly 2hp dc. The inlet is 5", so that is the size pipe I used. I found the straight pipe and the elbows at HD. Could not find 5" wyes. A local HVAC supplier had some made for me. I think they were $7.58 apiece. The only problem was I should have told them not to crimp them. They are made for heat and air, so they flow backwards to a dc.
Didn’t think about that when I had them made. I used 2 elbows in the turns. My blower is located outside the shop. The system does good, but I am sure it would be better if the crimps were the other way.

paul

[John Keeton]

Paul, you can undo the crimping pretty easily, and recrimp as needed. I used the round end of an anvil and hammered the crimp out of a couple of fittings in just a few minutes.

[Jay Yoder]

I checked with my Furnace/AV/ hvac friend and he can get me 26ga 6" for about $16 for a section of 5'-0" he also can get me wye's and adjustable 90's in 6" 26ga...i still have to design this system and then analyze the costs...there seems to be so many options, and just as many opinions! My initial thoughts are that i could get the straight lengths of 26ga from him and maybe the fittings from another supplier. Shipping on the straight lengths would probably be big $$$...

[Travis Porter]

I checked with my Furnace/AV/ hvac friend and he can get me 26ga 6" for about $16 for a section of 5'-0" he also can get me wye's and adjustable 90's in 6" 26ga...i still have to design this system and then analyze the costs...there seems to be so many options, and just as many opinions! My initial thoughts are that i could get the straight lengths of 26ga from him and maybe the fittings from another supplier. Shipping on the straight lengths would probably be big $$$...

I used metal pipe for my setup. I destroyed my hands (didn't wear gloves as I should have:(). I bought all my straight pipe at the borg 8", 6", and 4" and all of my 90's and wyes from Oneida which was not cheap. For the hvac stuff, make sure you get long radius elbows as the standard stuff is short radius and I was shocked at the diference in flow they make. A lot of the HVAC wyes work, but they are crimped backwards to what you would want so having the crimping pliers is a must.

Metal is nice, but it can be a pain to get going.

[John Keeton]

I checked with my Furnace/AV/ hvac friend and he can get me 26ga 6" for about $16 for a section of 5'-0"...
Prices may have changed, but when I did mine a little less than a year ago, I paid about $8 for a 5' section of 6", 26ga. snaplock. The 30ga fittings were cheaper than 26ga and I would not be concerned at all using them.

[Steve Kohn]

Prices may have changed, but when I did mine a little less than a year ago, I paid about $8 for a 5' section of 6", 26ga. snaplock. The 30ga fittings were cheaper than 26ga and I would not be concerned at all using them.


I almost totally agree with John above, with one exception. I have a metal ductwork system working off a Grizzly G1029 2 HP collector. Originally the inlet was 5 inch when I set the system up. All the straight pipe was 26 guage snaplock from the Borg and the fittings were purchased from Oneida.

A couple of months ago I needed to add a branch to the system due to the acquisition of a wide belt sander. I modifed the input to the DC to 6 inch by cutting out the cover plate, ran 6 inch to a PSI economy wye, and ran 30 guage 6 inch BORG snaplock across the ceiling (20 feet) to the sander. The system seems to move dust in an acceptable fashion and the pipe has not collapsed.

[Rob Cunningham]

. For the hvac stuff, make sure you get long radius elbows as the standard stuff is short radius and I was shocked at the diference in flow they make.

How large of a difference is there in airflow between long and short radius elbows?

[Chris Padilla]

Rob,

I don't have any numbers for you but the difference can be significant. In an ideal setup, there would be ZERO bends and transitions. As you add more and more bends and such, it increases turbulence and decreases performance. Bill Pentz probably has some numbers for you if you search his pages. It is something like 1 90 bend (non-long-radius) is equivalent to like 15-20' of straight pipe. If you go long radius (i.e. a gentle, smoother bend), it likely drops in half. Now I'm just guessing at this so confirm this for yourself.

Suffice it to say, changing things in your airflow stream as gently as possible (or practicable) is the name of the game.

For PVC, long-radius 90s are very expensive. You can get very close by putting 2 45s together at ~half the cost of a long-radius 90.

[Ed Hazel]

I checked with my Furnace/AV/ hvac friend and he can get me 26ga 6" for about $16 for a section of 5'-0" he also can get me wye's and adjustable 90's in 6" 26ga...i still have to design this system and then analyze the costs...there seems to be so many options, and just as many opinions! My initial thoughts are that i could get the straight lengths of 26ga from him and maybe the fittings from another supplier. Shipping on the straight lengths would probably be big $$$...


Oneida has 26 ga pipe 5"x60" for $15.80 plus they have 10%off right now and free shipping over $100.
I would think 30 Ga would be fine for 90's they have seems that add a lot of strength crush wise, put two together for a long radius.

[Paul Demetropoulos]

I checked with my Furnace/AV/ hvac friend and he can get me 26ga 6" for about $16 for a section of 5'-0" he also can get me wye's and adjustable 90's in 6" 26ga...i still have to design this system and then analyze the costs...there seems to be so many options, and just as many opinions! My initial thoughts are that i could get the straight lengths of 26ga from him and maybe the fittings from another supplier. Shipping on the straight lengths would probably be big $$$...
Jay,

That's great that your friend can get that metal for you, for some ideas for your design you might check out this thread, some good discussion about pipe sizing and drops.

http://www.sawmillcreek.org/showthread.php?t=103714

[Jay Yoder]

So if i get the straight lengths of pipe from him, what about elbows? where is the cheapest source of actual dust collection parts? I have checked out both Oneida and also Penn State Industries. Are the heavy adjustable elbows good? Is there much difference in airflow between the segmented bends of an adjustable elbow versus the stamped smooth elbows from say penn state industries? Do the stamped elbows match up with snap loc pipe or would i have to go with the spiral?

[Jim Becker]

Jay, check out Kencraft. They typically have good pricing on laterals and elbows that are designed for dust collection purposes, rather than HVAC.

[Pete Kurki]

Just wanted to second John's advice of staying away from the 30 ga stuff if you choose to go metal. Even if it worked OK with your initial setup, you would have to replace all your straight pipes if you found you are lacking CFMs and need to upgrade to a bigger unit.

A couple years ago I bought a 5 hp Pro 2000 from Oneida with most of the 26 ducting with the initial order. I was short one length of straight 8" pipe and used the 30 ga stuff instead of waiting for another week to get the piece from Oneida. I decided to test start the cyclone after I had installed the initial 5 lengths of 8" and 2 lengths of 7" pipe with the first two 5" drop downs into my machines. The drop downs were wide open;as a matter of fact I had not even installed blast gates yet. The 30 ga piece collapsed in a split second as soon as I had started the cyclone, while every 26 ga length before and after it held up without a complaint.

Based on what I have seen and heard, my very subjective opinion is that if you have a cyclone with 2 hp or higher rating that works ok with 30 ga pipe, either the hp rating was exxaggregated or there is something wrong with the cyclone or ducting design that reduces the power to start with.

Pete

[Jim O'Dell]

Jim,
I am using a Jet-1100 with canister filter. Where did you get your fittings? Did you have any trouble sourcing long radius elbows? or I guess the rough equivalent would be using 2 45 deg fittings together...I guess one solution to the 30ga dilemma with blast gates all closed would be to install a floor sweep that is always open...then again, i would prefer to just make sure a gate is always open...


Jay, I apologize, I haven't opened this discussion back up and hadn't realized you asked me a question.

I didn't even try to find long radius 90s. I took the information others had said and used two 45s with a short piece of straight between them where I could. I got all my 45s from McMaster-Carr. Good prices, honest shipping costs, and very fast service.
I got my straight pipe locally after a lot of searching. The first 2 sections I bought were IIRC about 19-20.00 each. I had to show them the pipe sitting in their yard!! The guy remembered me the nest time I went in a month or so later, and sold me the next 3 sections at 11.00 each. :cool: Almost made me wish I needed more!! :D Odd that this place doesn't have fittings...or at least doesn't think they have fittings. I say that because they didn't know they had the pipe! I bought the 6-6-6 wyes also from McMaster-Carr, but the two 6-6-4 wyes (about 20.00 ea) and the 22.5 degree fittings that I needed, I got from Lowe's. The wyes were easily half again the price of the 6-6-6 wyes from MC, and the 22.5 els were also more expensive, but I'm not remembering the specific prices.
Hope this helps. It might be worth asking your friend in the HVAC business where you can get spiral pipe from a local manufacturer. I've read where larger communities usually have some small shop that makes it locally for really good pricing, comparable to PVC, if you can find them. I would think it would be a lot stronger than snaplock. Jim.