Designing dust collection

@Jon @cfstaley and others who may have been involved in designing the dust collection setup in the woodshop - any advice for someone who has no idea what they’re doing and wants to design a solid dust collection setup in their garage woodshop?

I have a Laguna P-Flux dust collector and I’m getting sick of the rockler flex host sprawled across the garage floor - not to mention the dust collection isn’t awesome on a fully flex hose system.

If it helps, I’ve got a Sawstop with the built in router table wing, 12" Jet Jointer/Planer combo, Laguna 15" band saw, and Supermax 16-32 drum sander I’d like to tie into the dust collector. I also have a miter saw, oscillating sander, drill press, etc that I might want to tie in but can also get away with just using a shop vac for.

At home I just have one flex hose on my collector that I move from machine to machine with Dust Right quick-connect fittings. I basically use it like a giant shop vac. That keeps the plumbing simple and hoses short, and I’ve never had a problem with performance.

If you want something more fixed, small-shop dust collection is still pretty simple if you only run one machine at a time: your goal is just short run, smooth pipe, large radii. You could just run a 4" main around the shop with a sweep tee and blast gate for each machine.

If you want to go to the trouble, you can run an overhead. PVC DWV pipe seems to be common. Put your gates overhead to reduce the losses from the various connections. Then when you do go to flex, you’re only pulling on the local section.

Thanks both, I was afraid I wasn’t thinking through it enough, but this all sounds pretty straightforward.

PVC is notably quieter than metal. There are concerns about fire in PVC ducts- not because static builds up and starts a fire, that seems to be a myth. Rather, if your bit or saw strikes a steel screw, it can throw sparks and red-hot metal into the dust stream and that’s the ignition problem.

The ordinary steel seam ducting from hardware stores will work until you draw high static pressure, then it can just collapse. This problem will occur if no blast gates are open or a single duct is in use but becomes clogged with debris.

Steel spiral pipe will not collapse, but it’s much more expensive. Also more difficult to get ahold of. But it’s the right stuff for the job.

Dust Collection Research - Home has a lot of good info.

In particular, note that there is a critical air velocity needed to keep debris suspended and flowing. It’s air velocity specifically, not pressure drop. The critical velocity needed does vary with the type of debris. Fine sanding dust is easy. Harder stuff would be planer chips, and in some cases CNC router or table saw can make long strings or strips that require much higher velocity to hope to carry them away with airflow.

The critical air velocity needed is much higher for vertical lifts. So in general lifts are 4" pipe, which creates some undesirable flow restriction in the system but it’s essential to maintain flow velocity. Now, you might be able to lift with a single 6" pipe fanning out to 3x tools when all ports are open. But, if you close 2 of the 3 gates because normally you only use one tool, the suction at the tool itself will increase, but the air velocity in the 6" pipe will decrease and will not be fast enough to lift.

A system with blast gates needs to be evaluated for all its possible configs. e.g. if all gates are closed, will the system collapse its pipe? Or, if you have a big low-flow-resistance 8" horizontal trunk leading to a bunch of 4" ports but only one is open, will the flow velocity in the 8" pipe be high enough to keep the debris moving or will it just come out of the lift pipe only to stop and build up in the 8" pipe due to low air velocity there? Again, Bill Pentz has a ton of info there.

All good advice above. I’ve set up and reconfigured dust collection many times. Sometimes it’s easier to understand seeing it in person, so you’re welcome to come to my shop and I’ll walk you through why it’s laid out the way it is and what works / doesn’t work well.