What's inside
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Branch lines determine whether dust reaches the collector or settles in a hose, fitting, or machine. Plan them around the tools you use, the collector’s actual airflow, and the duct size each tool can support—not just where pipes look tidy. A modest system with short, sensibly sized branches often works better than a large network full of restrictive fittings.
Start with the collector and the hardest-to-serve tool
Before buying pipe, find the collector’s fan curve or airflow data and note its inlet size. A rating measured with no duct attached is not the airflow you’ll get at a machine. Duct length, filters, fittings, and the tool’s hood all add resistance. If the manufacturer provides only a headline CFM figure, treat it as an optimistic reference, not a guaranteed delivered flow.
Then identify the tool most demanding to capture. A planer or wide-belt sander usually needs more air than a random-orbit sander. Check the tool manual for its port size and airflow recommendation. A 4-inch port is not proof that the tool needs exactly 4-inch duct, and a large duct does not make an undersized collector deliver more air.
Measure the proposed route from collector to each tool, including vertical rises, elbows, and flexible hose. Put the longest or most demanding route on paper first. If it is too restrictive, changing the branch layout may help more than adding extra pipe to every machine.
Size each branch to the job
Use the tool port as a starting point, then compare it with the collector and the duct run. A short 4-inch branch can be a sensible match for a small collector serving one machine at a time. It is not automatically sufficient for a planer with a larger port or a long run. Conversely, reducing a large main duct to 4 inches at every tool can choke a system that has adequate fan capacity.
| Branch approach | Useful for | Main trade-off |
|---|---|---|
| Short, 4-inch branch | Small shops, portable tools, modest collectors | Convenient and inexpensive, but can limit airflow on demanding tools |
| Larger branch, such as 5 or 6 inches | Higher-airflow machines and collectors designed for larger duct | Costs more and needs space; poor reducers or an undersized collector erase the benefit |
| Flexible hose for most of the run | Temporary layouts or a single movable tool | Easy to reposition, but corrugations and extra length create more resistance than smooth pipe |
Keep flexible hose as short and straight as practical—often 2 to 4 feet is enough to allow machine movement. A long coil of flex hose can sharply reduce airflow and collect chips in its ribs. For fixed runs, consider smooth metal dust-collection ductwork where the collector and layout support it. PVC is sometimes used in hobby shops because it is easy to cut and inexpensive, but it can build static charge; use suitable bonding and grounding practices if you choose it, and follow local fire and building rules.
Lay out the branches to reduce losses
Keep the main run direct, with the collector positioned to avoid unnecessary bends. Take branches off the main with angled wyes rather than blunt tees where possible. A gradual 45-degree entry lets air turn into the branch more smoothly than a sharp 90-degree junction. Use long-radius elbows instead of tight plumbing elbows, and avoid stacking several bends close together.
Run the main past the machines and keep each branch short. Put a blast gate near each machine so unused branches can be closed. An open, unused branch is a leak: it draws air that could otherwise be moving chips at the tool. Choose gates that slide freely and can be reached without stepping around a running machine. A basic dust-collection blast gate is usually adequate; a premium gate is not worthwhile if the duct itself is poorly sized or full of sharp bends.
Design for one open machine at a time unless the collector is sized and ducted for simultaneous use. A branch plan that assumes two machines can run together may leave both under-served. Label gates if their positions are hard to remember, and leave access to cleanouts and joints that might need inspection.
Choose fittings and transitions carefully
Reducers are unavoidable when tool ports and ducts differ, but use gradual transitions where space allows. A sudden step-down can disturb flow and trap chips, especially when the larger duct is carrying heavy planer shavings. Avoid reducing the whole system to the smallest machine port. If one machine has a 2.5-inch port, give it a dedicated short adapter rather than shrinking the main line for every tool.
Buy fittings that match the actual outside or inside diameter of your pipe; dust-collection sizes are not always interchangeable with plumbing sizes. Dry-fit the layout before cutting, then seal stationary joints with appropriate tape or sealant. Leaks waste airflow and can release fine dust into the shop. Don’t permanently glue a section that you may need to dismantle for a blockage or a future layout change.
For a small shop with a modest collector, 4-inch dust-collection flex hose can be the cheaper, perfectly reasonable choice for short connections. Spend on smooth rigid duct only where long runs or repeated bends make the difference useful.
Test airflow and watch for failure signs
Start with one gate open and run the collector. Check the tool hood while making a representative cut; a tissue test at the port alone does not prove chips are being captured at the blade or cutter. Watch for dust escaping, chips lingering in a planer hood, or a hose that collapses. Those symptoms can indicate a restrictive branch, a clogged filter, a leaking joint, or a tool hood that needs adjustment.
Inspect the filter and collector bag before changing duct sizes. A loaded filter can reduce airflow enough to mimic a bad layout. If performance is still poor, shorten flex hose, open the intended gate fully, remove unnecessary bends, and check for a blockage at reducers or low spots. Do not assume a larger fan will fix a poor capture hood.
Dust collection does not remove every fine particle. Use a properly fitted respirator when the work or cleanup creates airborne dust, and keep the collector and ducting away from ignition sources. Plan branches so hoses do not cross walkways or create trip hazards; a clean airflow path should also leave a safe, workable shop.