Exploding PVC Dust Collection Ductwork?
PVC tubing is a popular and relatively inexpensive alternative to metal ductwork for dust collection systems, but some woodworkers worry that all that plastic tubing they have snaking through their shop will someday blow up or catch fire. Are there risks involved in using PVC tubing for dust collection? According to Woodworker's Journal Editor Rob Jonstone and widely-read woodworking author Michael Dresdner, the risks are minimal, in spite of what you may have heard.
Woodworking Question. I just got a dust collector for my home shop for Christmas. My shop isn't very elaborate (my wife calls it a "garage" - I call it my drive-in wood shop). While researching how to build up my system of tubes, I noticed most of the name-brand woodworking shops sell plastic dust collection tubing. Especially during the winter, the static electricity that builds up in this plastic is incredible and -- growing up near coalmines -- I learned that flammable dust and sparks don't mix. To avoid the possibility of blowing up, is it worth the time and money to set up a metal-based dust collection system, or just go with the fancy plastic stuff and ground it?
For that matter, should all the woodworkers out there with PVC systems put more effort into grounding them? A recent article showed a shop-built downdraft table hooked up to a plastic dust hose … is this a time-saver or time bomb? Then again, is metal tubing connected to a dust collector sitting on rubber casters really grounded or just a suspended capacitor looking for a ground?
Answer from Michael Dresdner: "This issue is one of the most hotly debated on Internet message boards. The best information from the most reliable sources I have seen is that, in most cases, you are perfectly safe running plastic pipe. Admittedly, if you can afford it, metal pipe is better. Plastic pipe may give you a shock, just like a shag rug paired with a wooly sweater, but it is not likely to generate a spark capable of starting an explosion."
Answer from Rob Johnstone: "Let me start out by saying that, in over 25 years of woodworking, I have never heard of an actual explosion or fire resulting from the 'static electricity on the plastic dust collection tubes' danger. Tons of ink (both real and virtual) have been spilled discussing and debating this 'issue.' With that said, if you are concerned about it ... ground the tubes with a wire running through the system. You'll feel better, the electrical supply company will thank you, and you can then be considered an expert during the next online 'discussion.' Did I mention that I have never heard of a problem with static electricity exploding dust in a plastic tubed system?"
If you want a little more in-depth look into the subject of dust collection, PVC and static electricity, read Rod Cole's thorough and well researched article, "Grounding PVC and Other Dust Collection Myths." The article, which you'll find posted on a number of websites including WoodCentral, goes just about as deep as most of us would ever want to go into the physical and electrical properties at play in explosions and fires caused by electrical field discharge. In the end, Rod agrees that the risk of explosion or fire involved in using PVC tubing for dust collection in a home shop is very low, and concludes that "the primary issue is to protect yourself from a shock."
Should you ground your dust collection system? Whatever the risks of explosion or fire, taking a "better safe than sorry" attitude and equipping your PVC ductwork with a grounding system will at least prevent you from suffering a nasty zap when you brush up against a dust collection port. Rod Cole offers a few directives for grounding a system toward the end of his article, and to make the project easier, Rockler offers a Dust Grounding Kit made for the purpose. Between the two, you'll rest a little easier and you'll be likely to spare yourself a few unpleasant surprises from your dust collector's ductwork.