Cleaning dust collection ductwork

[Alan Kalker]

My dust collection pipes (4" and 6") are clearly clogged as the suction has become minimal. Some of these are 20' long with turns. What is the best way you've found to clean out you pipes?
Thanks

[Lee Schierer]

On my 4" system, the first step is to empty the bin and clean the filters. Then open the far end of the pipe so it gets full flow. You may need to do this at an inlet on each branch.

[roger wiegand]

Assuming you'e checked the filters, have a look down the pipe and determine where the clog is, then take it apart and fix whatever is snagging the chips on the way past. Except in very rare circumstances (long curly shavings from a lathe, for example) blockages are almost always due to something sticking out into the flow path-- too long screw, bent end, whatever. A cheap boroscope can be useful to look in the pipes without extensive disassembly.

[Bill Dufour]

I would turn on the blower and run a plumbers snake or a electrical fish tape from each inlet.
BILL D

[Thomas Wilson]

Only jams I have had were thin ripped strips from table saw that hung up on a plastic y fitting that had crossbars for internal structural support of the fitting. I replaced that fitting with a better design.

Also, if you cut with a tool without turning on the collector or have flow directed to wrong tool, chips fill the tool pretty fast. Plug is usually really close to cutting source.

[Kevin Jenness]

If Lee's method fails try a long shopvac hose from each end.

Why is this happening? Clogged filters and poor duct design or installation are common problems. You may want to set up a manometer to give a visual indication of system performance and remind you to clean the filters periodically.

[Richard Coers]

Buy a bigger blower. If the ductwork is packed that tight, you don't have enough flow for the design of the ductwork. Eliminate as much flex as you can, and go to long radius elbows.

[Steve Jenkins]

I once had a rag sucked in and didn’t know it until it plugged up a few days later. Found out by taking ductwork apart at an elbow. The rag was hung up on a screw even though the screw barely protruded on the inside.

[Alan Kalker]

Thanks for the above responses. I have an Oneida system and it's pretty powerful. The dust collection barrel comes with an infrared sensor connected to a flashing red light. I should not have assumed it was working and should have checked the barrel first. Oops. The sensor had apparently failed and everything was backed up. It's a wonder I didn't burn out the motor or worse. Along the way, I did get one of those 8" flexible rods used to clean out dryer lint. It's pretty whimpy but did help clear out some the the backup. Anyway, the system is back to working like it will suck your face off if you get too close to the inlets. Now back to actual woodworking.

[Thomas Wilson]

The Oneida Dust Sentry adjustment is a tiny little slotted screw that is very sensitive. I have mine set so that it begins to blink at ~1/2 full. Blinking gets faster as the bin fills. I get nervous and dump the bin after a few more passes. It is usually 3/4 full or less.

My system, the 5hp Smart Gorilla, has strong air rotation in the drum. The suspended dust causes the blinking. I have considered some sort of baffle to settle rotation down. So far I just think about it.