Vacuum hoses come in many different sizes, and they often play a part in many people’s purchasing decisions when shopping for a new wet/dry or shop vacuum.
Smaller diameter vacuum hoses are often more maneuverable and flexible, not to mention lighter, and for certain applications there are performance benefits.
Larger diameter hoses can pick up bigger debris, and with less likelihood of clogging.
The other day, I talked about some issues I had with my Shop Vac, when using it to pick up water. Afterwards, I thought about some future testing I want to do, to see how its performance compares with other vacuum types.
With shop vacuum sizes, 2-1/2″ is a good size for general cleanup tasks. Sometimes a vacuum will come with a smaller hose, other times an intermediate size.
My Festool dust extractor has a 27mm hose, which works great with many handheld power tools, such as sanders. Smaller shop vacuums come with 1-1/4″ hoses.
What’s the difference between a 1-1/4″ hose, and a 2-1/2″ hose? The diameter is doubled, and so the cross sectional area is quadrupled. (Remember, the area of a circle is pi*r^2.)
I recently tried to split the vacuum connection of my dust extractor, so that it could connect to a portable table saw’s lower and guard ports. Most of the dust was collected through the 2-1/2″ port via my 50mm hose, and the 27mm connection was able to clear the blade guard port, albeit with much-weakened suction. Why? Because I was now asking the vacuum to work with 4.43X the hose cross section, combined, with the 27mm connection only receiving 22.6% of the full suction power.
Imagine you buy a small shop vacuum, and it comes with a smaller hose. What happens if you buy a 2-1/2″ hose to use with it? With the same suction power applied to 4x the hose size (remember, 2x diameter, 4x cross sectional area), the airflow velocity will decrease.
Some shop vacuums and dust extractors come with intermediate-sized hoses, for maneuverability and attachment benefits, without compromising too much.
With my dust extractor, I have found that a 27mm hose works great with sanders and my plunge-cutting circular saw. I bought a cleaning set, and it came with a 36mm hose, which works better with routers. Sometimes I will use it with the circular saw, and supposedly performance is supposed to be a little better. And then I have a 50mm hose that works even better for cleanup tasks. The 50mm also connects to the 2-1/2″ port on certain tools, such as portable table saws.
When using my 27mm hose with sanders, I often have to dial down the suction, or else there is too much suction power, and the sanding pad can “stick” to the work.
In my post the other day, some readers hypothesized that my use of a wet-rated filter had hampered the vacuum’s performance. While still possible, I think that the 2-1/2″ hose and large nozzles simply couldn’t produce enough velocity to perform as fast and effectively as I had anticipated. Switching to a Fein, with its 1-1/16″ (27mm) and smaller nozzle, resulted in higher airflow velocity.
I probably would have seen better performance from the Shop Vac if I had swapped things over, but the Shop Vac had other downsides that would have led me to reach for the Fein anyway, such as the lack of a good top handle.
I have taken hose sizing for granted. I figured it would help to create a visualization, since working out differences on paper (yay, math!) might not always be clear.
With my router table, I’ve been wanting to add a below-table box, to help better contain the dust. Most product manufacturers recommend their under-table dust accessories be used with a 4″ hose, but they don’t explain why.
Surely I can just branch off my dust extractor, right? Or even use a second one?
A 4″ hose is recommended so that it moves enough air to cool down the router motor, at least that’s the consensus on woodworking forums. If there’s not enough airflow, there’s no escape for built-up heat, and the router motor could be damaged.
Why not use a second shop vacuum or dust extractor with a step-up adapter? A 4″ hose is 60% wider, with 2.56X the cross sectional area. Remember, most larger shop vacuums and dust extractors are designed to work with 2-1/2″ hose diameters – at the most. There’s a good chance that there just wouldn’t be enough airflow.
Selecting the right vacuum hose for the job is tough.
A smaller diameter hose, such as 1-1/4″ or 27mm, will often work better with smaller handheld power tools, such as sanders, jig saws, and even circular saws (at least those with dust ports).
A medium diameter hose, such as 1-1/2″, 1-7/8″, or 36mm, is a good middle-ground for cleanup tasks, and tools produce lots of chips and dust that can clog smaller hoses, such as routers.
A larger diameter hose, such as 2-1/2″ or 50mm, are great for general cleanup tasks, and for connecting to tools with similarly sized dust ports. You don’t want to use a step-down adapter, if you could help it.
Use a small hose on leaves, and you’ll spend a lot of time sweeping over an area, and then cleaning out the clogs. Use a large hose on fine dust or water, and you might lose enough airflow velocity to hamper performance.
Update and More Hose Sizes
Someone asked about how 27mm, 36mm, and 50mm hose sizes compare.
What I’ve found, by measuring all the hoses immediately accessible to me, is that metric hose sizes are measured in terms of their inner diameter, while inch-sized hoses are measured in terms of their outer diameter and accessory connection size.
For instance, I measured a Shop Vac 2-1/2″ vacuum hose, and a Festool 50mm vacuum hose, and they both measured ~2.4″.
Wall thicknesses can vary, and as such, the diagram was always meant to be a rough visualization.
But, it seems fair to compare metric hoses against each other.