I am preparing to buy a new two stage dust collector from Oneida and like many people they don’t recommend using PVC due to the possibility of static charge inside the duct. However, I have also read that many people are still using PVC without any issues. My dilemma is that if I go with metal ducting it is just as expensive as the dust collector due to the size required for the ducting. What are your opinions and if I should be concerned with safety issues by using 6” PVC? Thanks
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I used PVC in my previous shop for many years without issue. I did yield to the cautions and installed grounding wires inside the PVC. at every joint, there a 1/16" hole where wire came out and wrapped around a sheet metal screw. Then a jumper to the other side of the fitting, connected to the next run. Grounded at the collector end, and a connection to the blast gates. Never an issue. Cost was minimal, as I used an electric fence wire, really cheap stuff.
My old system was all pvc, my new one is a mix of metal and plastic.. no special efforts towards grounding on either. Never had any issues or a single static shock.
When I used my shop vac hooked my DeWalt 735 planer that had a cyclone atop a 5 gallon bucket, I got a really nasty static shock when I dumped it out right after filling it up. Much stronger static shock than anything I’d felt before. It’s made me cautious. I just finished installation of my 3 HP Oneida system. I’m fortunate in that I have only two tools (bandsaw, DeWalt 735 that need dust collection). As such, just MagnaPort clamps and less than 10’ of the accordion style hosing Oneida sells with copper wire in it. If I were to run a duct system, I’d likely want metal. All based on zaps from static from the Shop Vac set up. I believe what others have said as well. Then again, my nickname in grad school for chemistry was Captain Caution. I’d see some bad lab accidents as an organic chemist at the time. I tend to be overkill on most safety things or want to over engineer out potential issues.
I have had PVC in my shop for 7 years now and just one time got a little shock closing the gate on my DeWalt 735 after use. It wasn't any more then what you can get from new carpet and I attribute it more to the fan that is on the 735 to blow the chips out more then the possibility of it being from the PVC.
There are no safety issues using PVC pipe for woodworking and there is no need to run ground wires or anything silly like that.
Whilst there are anecdotal reports of occasional mild shocks from PVC dust piping, I have never experienced one. I live in a fairly dry area with low relative humidity, and even so never once a shock, not even after trying to get one after planing piles of oak.
There is also no medical danger from such shocks if they do occur as though the voltage is very high, the current is minuscule.
https://store.workshopsupply.com/catalogue/pdf/DC-Myths.pdf is an excellent treatise on the matter by someone who actually knows what he is doing if you want to get the real lowdown on it.
The TLDR is that it is not possible to generate enough static to make a spark and it is so close to impossible to make a combustible mixture that there is no risk in the home shop setting.
Logic also comes into play - home vacuum cleaner hoses are plastic. Almost all home shops use PVC pipe for cost and easy availability reasons. Where are the fires? How many cleaners are killed by exploding Hoovers each year? How do people with shop vacs connected to routers survive? - This is a theoretical problem that has no actual impact in the real world.
If you are setting up a 36" wide belt twin sander which can remove a couple of pounds of dust a minute, you should definitely be looking at metal ducts and a proper explosion mitigation plan from a professional, but if you can afford that machine, you already knew that, and the cost of the ducting is trivial in comparison.
Thanks, you are right, my gut has told me it isn’t a real issue, just people thinking of an extremely remote possibility to completely rule it out. I did see a YT video of a full time electrician and part time woodworker who made a video proving it was not possible. That said, I felt I should ask the woodworkers community whom have PVC their opinions. And yes, the cost of the Oneida system is way overpriced and the fact that ducting cost just as much is unrealistic at $8k for collector and metal ducting. I can’t afford both, which is why I am looking for other options. Thanks for your opinion.
Also I want to thank Chet, mj, and Mitch for your opinions as well.
I switched from 4" PVC to 6" metal and upgraded my dust collector a few years ago. I had bare copper wire inside and outside the PVC grounded to electrical outlets. I don't think it was needed for reasons already stated.
At the time (2019?) I switched, 6" metal spiral ducting was less costly than 6" PVC, by quite a bit. I have not checked lately.
Thanks MRM, Do you think the metal ducting performs better than the PVC?
PVC for 20 years in multiple shops. Never an issue. Those against it either sell metal duct or have bought it ;-)
Oh boy. Well I have a mix ox pvc and metal. I attached a ground wire to each metal blast gate out of pure paranoia rather than and convincing articles or studies. And my main 7" line is two concrete form tubes. "This is a temporary setup until I can drop the coin for a 7" metal line" I said to myself 5ish years ago. It might just stay there. I've had no issues with my hodge podge setup. I'm mostly self taught so take that into account.
I ran mostly 4" PVC with 6" trunk lines about 30 years ago. After I got the system running, I tried it out by pushing the accumulated shavings under Powermatic table saw into the duct opening for it. Started seeing orange flashes. Multiple ones. Stopped the collector and started running bare copper wire from machines along outside of pipe to collector. Attached it every 4" with short sheet metal screws that poked thru the PVC a bit, but not enough to snag large chips. I don't know if that is as good as wire inside the pipe, but I can tell it is undamaged.
The answer to the first question is Yes, it will generate sparks.
The second question is How can I guarantee that I will never have an explosive mixture in the pipe? My guess is that while working with some machine or hand power tool, I am not likely to generate an explosive mixture. However, if I am cleaning up after a messy operation with lots of dust, it seems more likely. The consequences of a fire are potentially severe.
It is hard to say what would have created those flashes, but certainly not static build up, which would be blue in general and too small to be visible in all but a darkened environment.
Sadly the grounded wire and screws inside the tube do not do anything other than reduce the risk of a shock from the PVC to your finger, but at least it is cheap. The physics of it are discussed gently in the linked article in my earlier post.
Whilst a reductionist perspective on risk is very useful as a thought model, in practical terms it has little value. If you have several pounds of fine sanding dust on your floor, then you have bigger issues with fire risk than your ductwork!
The myth part is about grounding the PVC by running a wire, unless the PVC is conductive (it’s not) the only area grounded is the wire.
I read years ago on the Bill Penz website, he suggests grounding by applying a strip of aluminum adhesive tape inside and out. Inside is a bit tricky but possible. I use PVC but have not had issues with static unless I open up the line and run the collector. I haven't bother with the tape or wire
Penz suggests using sewer and drain pipe for cost savings.
Some years back, there was a short article that stated there is no danger of explosions from a home shop using PVC ducting.
Metal ducting may not be much more than PVC. I've found metal fittings are much more expensive.
As
Hello everyone, thank you all for your input. After much research that I have done and what I have received from others, I can without a doubt in my mind say that there is no proof that PVC ducting is not a viable and safe solution for a home shop dust collection system. I will be using a 6” PVC ducting system for an Oneida V3000 Smart Boost dust collector. For your info, I found a very informative article written in May 2000 updated in Nov 2001 from Rob Cole, MIT, Lincoln Labs. This is a very well researched article with detailed analysis that even a layman can understand. “Grounding PVC and Other Dust Collection Myths”. See attached article
I just read the article. It is well done for sure.
Be aware if you use aluminum blast gates you can get shocked if the humidity is low.
I have had a 3hp cyclone dust collector w/ 7 1/2" intake with PVC pipe for 30 with grounding wire. A 3hp+ cyclone dust collector w/ 7 1/2" intake is not the same as a 1 1/2 hp system.
Add a wire to ground!
Large volume of sawdust will cause a lot more friction. So when I put my system in I thought that start a fire or cause someones heart attack would cause a insurance rate increase that would be way beyond the cost of some wire. Not to speak lightly of fires or heart attacks.
John
If I had a choice, I'd use steel ducting. It definitely is harder to install but it eliminates some of the issues people are concerned about. Oneida wouldn't recommend it if it wasn't better. (Just my opinion....)
I wish MythBusters was still making new episodes. Would be really nice to have them test this one. I worry about it but then again, I tend to worry about a lot of safety relegated things. Then again, I have personally known a few chemists missing limbs, blind in an ear, eye, burned to within inches of their lives. All of this was in my early 20s (back in the 1990s). Kind of hard to get that out of my mind when it comes to other fire or explosive situations.
Too funny Joe. But there will always be things we take for granted or push it to the limit. In the 90s I was in Special Forces blowing in doors and throwing grenades all within feet of me. I think back sometimes and ponder no wonder I get migraines, have Tinitis, and wear hearing aides - go figure. And now, look at how many of us are discussing air flow through PVC ducting - lol sure wish I would have had more concern back in my ARMY days and protected myself better. But, I know better now and I have to do whatever I can to filter the air I am breathing.
I put 6" PVC under the concrete slab in my shop when built (metal was not considered since it's buried). I have a Laguna 3hp cyclone and have never had an issue in the 5 years in the new shop. I did get a slight shock from my 735 planer one time and installed a ground wire at the exhaust duct and have not had any issues or shocks since. Based on the cost savings with going the PVC route, it was an easy decision. Yes, Oneida recommends metal ducting as that is what they sell for a premium price.
I have the inlet to my small particle collector low in the room because dust particles tend to fall down and the outlet high with HVAC duct connecting them.
I have no particular empirical evidence that this works better but that what I did this time. FWIW
The reason I did this is the sun was streaming through the windows one morning and the dust was just slowly swirling around towards the collector. It seemed like if was just suspending the dust in the air more than clearing it out.
I also use 4" PVC pipe for fresh air supply. I took an old furnaces fan & Inducer motor and connected it to PVC then to 4" flexable dryer pipe then to 6001 filtered respirator. Inlet is high on prevailing windward side of the shop
Best thing I ever did for my lungs and brains gray & white matter as well as my cerebral fluids.