# 3 inch PVC for dust collection



## djonesax (Mar 3, 2008)

I have a steel city 1250 CFM collector. I am running about 40 feet of collection ducting out of PVC. I understand the risks of static build up with PVC but I am a weekend warrior and I have read that its not a concern for people like me. I got my PVC at home depot. They didn't have the thin walled 4" pipe so I got the regular 3" pipe. I figured the 3" would be easier to work with anyway. My concern is the CFM drop I will have using the 3" versus 4". I think it will be OK but I hate to get it all assembled and realize it is not. I will have 4 drops all on quick disconnects and will travel maybe 50 feet including the drops and ceiling runs.

Any thoughts?

Thanks,

David


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## woodnthings (Jan 24, 2009)

*Main duct size*

Quote: 
M1911Bldr 
Junior Member
*Watch your plumbing (main run) size!* I installed a Shop Fox 1 1/2 HP DC in my shop and used 4" sewer/drain pipe. It worked OK but left fine dust all over. I recently upgraded to 6" pipe and WOW what a difference. My main run is "not properly designed" as it runs linearly through the shop with balst gate ports added to the sides in the tool locations and it runs "up and over" to get to the other side of the shop. I don't have any problems with pipe/air velocity carrying fine dust to the DC and it improved airflow at the collections points DRAMATICALLY. I installed a Thien separator in the metal ring between the upper and lower bags and installed a Wynn 35A poly filter in place of the upper bag and a "paddle cleaner" inside the filter. I can do the "white glove inspection" test on the DC itself and there is no dust at all on the unit. 5" pipe might give better vertical lift if you need it but 4" pipe will severely restrict your airflow.

Based on this I would not recommend the 3"...bill


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## rrbrown (Feb 15, 2009)

Bill I have the same DC and have 4" sewer for all duct work and my home made separator. I notice a little dust but only at the TS and BS and its not very much. I like the answer you gave but I have one question. How long is your main line? Mine goes up 6 ft then over in either direction like 20-25 ft. The TS is at the collector so its like 7' run of 4" flex hose. I plan on making an upper arm for my TS like yours with it connected to a shop vac but if I have room to improve my system I might look into it.

I also think 3" is way to small.


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## woodnthings (Jan 24, 2009)

*Richard that was a quote from M1911bldr*

It's not my system. I just remembered it in the discussion of duct size and searched it here. I hook my collectors directly to the machines with 4" flex hose, so I don't have long runs. I'm still planning the location of machines in the shop so it's best for me to have mobile collectors or multiple ones at this point. I'm working on redesigning the separator for my collector. I'll post a picture...so far a chicken feeder, a cardboard drum and some flex hose. I need a deflector. I know Phil Thein? ...http://www.cgallery.com/jpthien/cy.htm, 
has a good design for a separator lid, but I'm trying my own ideas. :laughing: bill



rrbrown said:


> Bill I have the same DC and have 4" sewer for all duct work and my home made separator. I notice a little dust but only at the TS and BS and its not very much. I like the answer you gave but I have one question. How long is your main line? Mine goes up 6 ft then over in either direction like 20-25 ft. The TS is at the collector so its like 7' run of 4" flex hose. I plan on making an upper arm for my TS like yours with it connected to a shop vac but if I have room to improve my system I might look into it.
> 
> I also think 3" is way to small.


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## rrbrown (Feb 15, 2009)

Bill here's mine. Oh I think that's plagiarizing if you don't say your quoting someone else. :laughing::laughing:


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## woodnthings (Jan 24, 2009)

*Interesting approach*

I'll post a picture of mine as soon as I get it patented and sell the first 100,000 :laughing: bill


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## Woodcutterron (Nov 21, 2009)

I have to say, using PVC pipe for dust collection systems is never a good idea, even for a 'weekender'. I'd ignore any advice from anyone who told you that static charge buildup is not a concern.

What that would be akin to is smoking while working around a bucketful of gasoline. Sure, if you're "careful', physics would dictate that in a perfect world, it would never be a problem. After all, you can chuck a lit cigarette into a bucket of gasoline, and 99 out of a hundred times, the cigarette will simply go out.

This is NOT one of those "well an airplane could fall out of the sky and kill ya" things. You would be putting you and anyone in your shop at serious risk every time it was fired up. One thing to keep in mind is that static charge can "accumulate". This is why during the dustbowl years, farmers were scared to touch their metal farm equipment after a dust storm, as the static charge buildup could knock a guy unconscious.

Another thing is that even weekend warriors occasionally take on a project that can make a LOT of dust and woodchips. Now I know some folks have gotten away with using PVC for dust collection systems, sometimes for years. Unfortunately, some don't. And in this case "beating the odds" could prove to be a serious or even deadly problem. This would actually be exacerbated by the use of Scedule forty, which when it explodes, can create projectiles with enough mass to be seriously injure, or even kill. 

I read in some magazine somewhere about running a ground wire through the system to eliminate this risk. The problem is . . .that it isn't that simple. Designing a proper grounding system for this type of use is actually fairly complex. Luckily, the magazine printed a notice a few months later and reinformed their readers that it is ALWAYS a bad idea to use PVC in a dust collection system, and that running a wire through it is not an adequate safeguard.

In a nutshell, the only common sense thing to do is forget about using PVC tubing for a dust collection system, particularly in light of the reality that there are plenty of options that are MUCH safer and not really that much more costly.

The last thing I would want to do is say be building a couple of tack trunks on a cool day with 25% humidiy, buzzing boards through my planer, . . . . . then BOOM.

One does NOT have to take my word for it either. Simply call the Manufacturer of the pipe, or a professional in air handling, and tell them what you intend. I can pretty much guarantee this is the response you will get: 

Who knows, you might get away with it for years . . . but on the other hand . . .


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## Gerry KIERNAN (Apr 20, 2007)

I would definitely try to run bigger pipe for a forty foot run. Three inch for your drops should be okay for the machines that don't produce large volumes of chips/dust, but your main would be better if bigger. The more volume of air you can pull through your pipe the better will be dust collection. As mentioned, a cyclone style seperator would also be very beneficial. 

Gerry


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## djonesax (Mar 3, 2008)

I am probably the worlds worst at knowing in my gut something inst right and then doing it anyway. I had all the stuff and just wanted to get it done so i did it anyway last night. So far its not that bad. The planer is fan assisted so I wasnt worried about that. The jointer seems to clear out well. My table saw was using a shop vac before and it was OK. The DC with 3" pipe works much better than the shop vac so I'm ok with that. The only thing left is the miter saw. The dust hood and a 4" hose worked fairly well or as well as it could because the miter saw is a hard one to catch dust anyway. Thats the only one I am worried about right now.

The thickness planer is right beside the DC. So thats 6 feet up the wall, 4 feet over, and 4 feet down for a total of 14 feet. Then the Jointer is beside the planer on the same run for a total length of about 22 feet. The the table saw is one the other side at about 25 total. The miter saw is about 33 of pipe away.

So far have ran 50 feet of PVC and hose. I have about another 15 feet left to finish the miter saw.

David


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## rrbrown (Feb 15, 2009)

Woodcutterrone first off why there is a so called explosion risk I as many have searched the net and asked for proof of an explosion. There is not one documented case of this explosion other then in some manufacturing plants. Those examples were not related to pvc piping but rather just dust explosion. 

Although the magazine which I believe was Wood or Popular Woodworking changed their opinion on this issue, it was baseless and probably done just as all medicine labels say death is a rare side effect, "to cover their a$$". I bet you still take Tylenol or Motrin even though they have multiple documented cases of death because of them.

Lastly although you are entitled to your opinion by all means. I prefer you "show me one documented case involving pvc and a static dust explosion" before saying it is as dangerous as smoking by a bucket of gasoline. There is no proof of static explosion in this context only theory where as there are numerous accounts of fire and gas. 

*David if you live in a dry climate it wouldn't hurt to add a ground wire to the ducting, Here in south Louisiana it's never a dry climate so I don't worry about it at all.
* 
*Only the facts please*


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## Woodcutterron (Nov 21, 2009)

Unfortunately, to the best of my knowledge anyway, there is no organization collecting and keeping such statistics. There is something I read awhile back on it by a guy named Cole (?), it was by no means the last word on the topic. To be honest, I expected someone to bring it up. Unfortunately, while the guy did do a lot of looking, it seemed more of a guy trying to support a conclusion he had already made and the lack of statistical breakdown handily supported his conclusion. He was an accountant or mathematician or something as I recall, and I do remember finding it odd that he seemed to focus solely of CFM in his calculations, while _velocity_ of moving dust is also an important factor in estimating static charge buildup. Further, humidity levels, as well as the type of wood dust would be important considerations. None of these important variables were even mentioned in his "study" as I recall.

A quick check at the OSHA site did reveal they don't specifically have a rule against the use of PVC piping, but the language is cautionary, and Californias OSHA does in fact prohibit it's use in dust collection:

_"*Dust* collection air and material ducts and flexible hoses should be made of metal or other conductive material that is bonded and grounded to prevent static electricity buildup from the airflow. Nonconductive flexible ducts and hoses may be used for final machine connection if they are the minimum length required to operate the machine, and if bonding to ground is maintained. PVC pipes can’t be used as ducts."_

Here's a link to an Air Handling company and what they have on their website, for whatever it's worth:

http://www.dustcollectorexperts.com/blog/dust-collector-ductwork/

As unpredictable as static electricity is outside of a Lab, it really isn't worth the risk.Again, when one considers there are a number of better solutions to ducting.What I do know is static electricity and wood dust aren't a great combination. 

I'm also aware, as a former firefighter myself, that many, and probably even most accidents of this type would likely go unreported unless the structure caught fire or there was a serious injury. Being that the "explosion" would be of a very short duration, often it might only scare the begeebers out of whoever was around. Generally, only 'the big ones' get reported. Small fires gotten under control by homeowners, shop employees, campers etc. more often than not go unreported. Again, this type of accident lends itself quite well to underreporting. Short duration of event, as well as the "embarrassment factor" contribute to lack of statistical data, as does this type of event being uncommon enough that it is likely lumped in a "general cause" generic classification in a small shop scenario.

I suppose the long and short of it is you'll likely be fine. For me though, "likely" isn't particularly attractive, in light of the easily installed, reasonably priced, and more efficient alternatives.

For the record, you boldly state that there isn't one documented case of this happening. How do you know that? How hard have you actually looked? Where did you look? While the list keeps getting shorter, there is still some data that isn't readily available simply by hitting the google button.


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## woodnthings (Jan 24, 2009)

*Here's a link to a great article on static in DC systems*

This discussion comes up repeatedly here and other forums and I doubt the debate will ever be settled. http://www.woodworkingtalk.com/f7/good-dust-collector-11975/ Read posts 5 and 6 here. Many here use the PVC or ABS for DC systems with no problems. Many here advocate the use of metal piping. 
The conclusion seems to be for a small shops used occasionally PVC is not a problem. For larger shops with employees better safe than sorry, use metal piping if not already required by code. I don't think there is an absolute answer to this. Here's the link and read this man's entire site he is a genius....radially expanding dining room table... http://www.waterfront-woods.com/ 
scroll the left side to get to "Static in Dust Collectors"
Here's one of our own threads: http://www.woodworkingtalk.com/f2/dust-collector-grounding-13151/
BTW This post was originally about the size of the PVC, rather than whether to use it or not, if I recall.  
OMT The next issue that will arise here is what "dust" is.... There's 2 types of material that DC systems collect, dust and chips and they are different, and can be removed or managed differently. The chips from a jointer or planer may clog a smaller diameter system if a significant amount is generated and there are too many 90 degree turns and depending on the type of wood, some wood chips spiral and clog easily. The fine dust from a table saw (on my table saw I use both a overarm collector with a shop vac and a 4" DC hose on the bottom) or miter saw will be OK in a smaller diameter system. So it may depend on which machine you are using which size will work best. JMO


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## djonesax (Mar 3, 2008)

I finished the project yesterday and everything works. I think the miter station had slightly better collection when I had a 4 inch hose connected directly to it but it's not too bad. Everything else is satisfactory and I don't know if I would be able to tell a difference with 4" pipe. I am sure that if would have been better with larger pipe but it works... I did experience my first little shock. I only ran a few passes through the planer and then touched the hose and got a little nip. Nothing painful but enough to consider a grounding wire.



David


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## Colt W. Knight (Nov 29, 2009)

I just read an article in one of the big wood working magazines reccomending the use of 6 inch metal chimney pipe for the main dust collection. They raved about the improved air flow and ability to pipe shavings and dust effectively.


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## Colt W. Knight (Nov 29, 2009)

I have a hard time believing that pvc and sawdust is going to cause an explosion. Coal dust, yes.


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## Woodcutterron (Nov 21, 2009)

What about sugar dust and corn dust?


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## rrbrown (Feb 15, 2009)

Woodcutterron said:


> What about sugar dust and corn dust?


OK I don't think he will be cutting sugar cane or corn so no problem :laughing:


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## Colt W. Knight (Nov 29, 2009)

I would be more likely to believe sugar or corn dust combusting because of its chemical nature. Im not saying that you couldn't make sawdust cumbust under certain circumstances, but I just can't phathom how it would happen in a practical shop dust collection system.


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## djonesax (Mar 3, 2008)

This may sound crazy but can I measure the CFM of the system by timing how long it takes to fully fill the filter bag if I know the cubic feet of the filter bag?


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## woodnthings (Jan 24, 2009)

*Only if you're filling it with air!*

Cause that's how DC's are rated, not by volume of material per minute, and different materials would fill at different rates, but it would be nice to know, whether it's a 1 beer or 3 beer wait time.....until the bag is full. :laughing: bill


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## rrbrown (Feb 15, 2009)

woodnthings said:


> Cause that's how DC's are rated, not by volume of material per minute, and different materials would fill at different rates, but it would be nice to know, whether it's a 1 beer or 3 beer wait time.....until the bag is full. :laughing: bill


That would also depend on how fast you drink beer.:laughing: 2 for you might be 3 for me.


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## Colt W. Knight (Nov 29, 2009)

Do we have to have an excuse to drink beer?


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## Woodcutterron (Nov 21, 2009)

I don't cut much sugar or corn either, heheh. Lets look at what we have:

1) 99% of wood dust is considered a class II explosive material

2) PVC pipe is highly flammable_ itself_

3) PVC builds _and often retains_ a static charge for a number of days, and this charge_ can accumulate _and build

4) When pressure failure occurs with PVC pipe, it breaks into high velocity sharp shards. (seen this myself with an air compressor and a potato gun . . another story)

5) California OSHA already completely restricts PVC pipe from dust collection systems under their jurisdiction . . . large and small.

6) As of 2 months ago (October, 2009), OSHA (nationally) has begun citing businesses for using non-conductive ductwork, specifically mentioning PVC Pipe, even for systems generating less than 5000cfm 

7) Most small shop fires/explosions go unreported unless catastrophic

8) No Organization, not even OSHA, keeps statistical records of all shop related Explosions/fires . . .even the minority that are actually reported to authorities.

9) The most quoted "study" I've seen on the net declaring PVC a minimal risk for dust collection . . . was conducted by a Math Teacher/hobbyist woodworker

10) 99 out of 100 times, if you flick a lit cigarette into a bucket of gasoline . . . it simply goes out. (Anyone who doesn't see the relevance to #10, ask someone else)

But . . .we can save fifty bucks by using PVC Pipe instead of metal ductwork since the odds are "pretty good" that we won't blow ourselves up running class two conflagarant/explosive dust through flammable, static-filled tubes. I've got the extra fifty bucks, luckily.

I do agree though the only excuse I need to drink a beer is that hey . . ._somebody_ worked hard to make that beer, the least I can do is drink it!


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## Woodcutterron (Nov 21, 2009)

I didn't add this to the list above as it isn't so much a "point", but might be of interest to some folks.

It's an OSHA press release from about 3 weeks ago:
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=16740

From the Federal Register, dated November 10th, also about 3 weeks ago:

http://www.smartpdf.com/register/2009/nov/10/E9-27003.pdf


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## djonesax (Mar 3, 2008)

woodnthings said:


> Cause that's how DC's are rated, not by volume of material per minute, and different materials would fill at different rates, but it would be nice to know, whether it's a 1 beer or 3 beer wait time.....until the bag is full. :laughing: bill



Of course I'm talking about air!  Which is why I said "filter bag" meaning the top bag. By the time the top bag / filter bag is completely full with air, I would assume I should be able to divide the cubic foot volume of the filter bag by the time it took to stand it up. That would tell me the CFM it was able achieve through the 3 inch pipe. I was just wondering if there was any flaw in my thinking.


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## djonesax (Mar 3, 2008)

I really cant see the pipe exploding. The only places that are glued are the drops so they wont fall out. If there were an explosion inside the pipe it would just disconnect the pipe. The potato gun is a good example. A shot of aerosol will dislodge a tightly jammed potato before blowing up the PVC. I only use the DC for the Planner, Jointer, Table Saw and Miter Saw. I use my wet/dry vac for sanding. From what I understand its the small particles that set the stage for ignition which come from the sander. I'm going to submit this to MythBusters!


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## Gerry KIERNAN (Apr 20, 2007)

Colt W. Knight said:


> Do we have to have an excuse to drink beer?


No!:thumbsup:


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## Woodcutterron (Nov 21, 2009)

I love Mythbusters, heheh. I have seen them blow it though. They supposedly "busted" a myth that the idea that giant chunks of wood and splinters produced by a wooden ship getting hit broadside with a cannonball could kill sailors. 

They suspended a mockup of a section of a ship hull suspended from cables or chains or something. They then took I believe a 3 inch bore cannon, shot the 6 foot by 6 foot (a guess) 'ship hull with it. Didn't produce deadly wood chunks. They declared the myth "busted". But . . . 

There were numerous problems with their methodology. For one thing, that little hull mockup recoiled back substantially upon being hit. A full sized ship would not have done this. Anyone who has ever used a loose bedsheet hanging over a rope for a BB gun backstop knows even a little "slack" absorbs a lot of energy. Further . . .Naval guns don't have those tiny bores. For example during the civil war, those dudes were popping each other with 16 inch bore Dahlgrens, 7 inch Brooks rifles things like that.

To further bust the idea that the myth was busted, one needs to look no further than Ships surgeons records. By the time of the Civil war, (and even the revolutionary war, for that matter) these records were quite detailed and thorough. And these logs are filled with mythbusters-busting descriptions of these types of injuries. I'm aware of this because I used to volunteer at the Civil War Naval Museum in Columbus, Ga. I've actually fired an original 7 inch Brooks Rifle removed from the C.S.S. Jackson Ironclad.

Our _blanks_ for that naval gun consists of five pounds of Black Powder, and "in the day" They would fire a 100-140 pound projectile sitting in front of 15-20 pounds of Powder. Mythbusters really should have checked with us, heheh. I've knocked back more than a beer or two with one of the foremost experts on Civil War medical history shipboard after a reenactment, I even made him a "retractable wood sliver' to use in his impression, so it looks like he's pulling it out of a sailor. 

I've kinda digressed a bit, I only point this out to demonstrate that Mythbusters isn't really "the last word" in definitive finding of fact.

Just for the heck of it, here is a link to a Video of us firing the HUGE gun. Not sure I'm here for this one or not from the video. I am on the museum website though, heheh, modeling the neckerchief
I also got my "5 seconds of fame" on The Military Channels "weaponology" series.:boat:
If you ever get to Columbus Ga by the way, the Museum is first rate, do yerself a favor and check it out. On a humid day, you'll actually get to smell the REAL civil war. They have the entire hull of the C.S.S. Jackson Ironclad there, burnt to the Waterline by the Confederates themselves at the end of the war to keep it out of Union hands. The smell of the charred wood still lingers 140 years later.


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## woodnthings (Jan 24, 2009)

*Very interesting and informative ron*

I searched "wood dust explosions" and found this site: http://dustexplosions.blogspot.com/2008/08/dust-collector-fire-new-jersey.html
Like I said earlier this issue will never be settled in a forum. The real proof would be if someone who had an actual wood dust explosion in a PVC system, if they are still standing, to chime in here with a complete analysis of the incident.
That's probably not going to happen. Mythbusters might take on the challenge however, and if their methods are correct, prove or disprove the theory. It would seem there is enough interest on this issue to warrant some sort of study. :thumbsup: bill


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## djonesax (Mar 3, 2008)

Woodcutterron said:


> I love Mythbusters, heheh. I have seen them blow it though.
> 
> They declared the myth "busted". But . . .
> 
> ...



There is just no pleasing you! :no::no::no:

Just kidding. I mentioned MythBusters as a joke and not as a means to an solid verdict. I often don't agree with the way they test stuff either but they make some nice explosions sometimes.


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## Doug4566 (Dec 18, 2009)

Here is my two cents. I use 4" pvc on a 1.5 HP system with a 20 foot run and 4 gates (sander, planer, joiner table saw). I layed bare copper wire throughout and grounded it to a metal wiring box. I have not had one tiny twinge of static, even in the winter. When wallboarding my shop last winter I stood on an aluminum step ladder using my shop vac and a drywall sander attachment to sand the ceiling and got some of the biggest static shocks I have ever experienced when the hose would periodically brush my leg. So the fact that i never got a shock from my dust system makes me feel pretty safe.
Doug4566


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