In our recent head-to-head comparison of the best dust collectors among OSHA-compliant models, two numbers were very important to us: CFM and water lifters. But which is more important when it comes to CFM on a dust collector vs. a water extractor?
The answer is a little bit of both.
Table of contents
- Understanding CFM on Dust Collectors
- Understanding Water Lift on Dust Collectors
- Final Conclusion on CFM vs. Collector Water Lift
- related information
Understanding CFM on Dust Collectors
CFM seems like a sexy number to consider for both vacuums and blowers. In both tools (and vacuums), CFM stands for cubic feet per minute and is a measure of how much air the motor sucks in per minute.
Let's take Makita's VC4710 dust collector as an example. It has 135 CFM. In other words, it sucks in enough air every minute to fill a cube about 5.1 inches on a side. Now this is very useful – if all the stuff you want to collect is floating in the air.
Essentially, CFM is what keeps the material moving after run. The larger the CFM value, the larger the area that the dust collector will affect during use.
Understanding Water Lift on Dust Collectors
Suction measurement can take many forms, but you'll usually think of it as water lift or some form of pressure rating. A quick google search will allow you to convert pressure measurements to water lift – just make sure you double check the units for the correct conversion.
Water lift measures the magnitude of vacuum suction. As the motor pulls the water up the pipe, gravity tries to pull the weight of the water back into place. Eventually, they meet in the middle when the duster is carrying all the weight it can. It's not uncommon for vacuums to be able to pull 90" – 100" like the vacuums in our shootout did in static water lift tests.
Editor's Note: Tube diameters vary. Note that our shootout results are based on 2-1/2" OD tubing and do not necessarily match the manufacturer's stated test results.
The importance of water lift is that the stronger the pull, the more debris the vacuum will collect. So when I say CFM is great for all the debris floating in the air, it's true. But you need suction to move anything that isn't floating.
It's a crazy thing – the suction needs to be very close to what it's collecting. Our duster will begin to pick up wood chips from the floor when they are about 1-1/2 inches from the floor and concrete dust when it approaches 1 inch. But it's most effective when the nozzle is only 1/2 inch from what you're trying to collect. So, the smaller or lighter the particle, the easier it is for your dust collector to collect it, but as the particle size increases, proximity is critical.
CFMs and water extractors must work together to be effective dust collectors. Obviously, the higher the number, the better both values. But like we saw in our cordless hair dryer shootout, it's better to have a balance of the two than to have one rated high and the other low. So don't be fooled by just looking for the largest CFM number you can find. Compare suction (water lift, pressure) values to see which has the best balance in the category you are considering.
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- Choose Dust Bag
- How Hoses Affect Performance
- OSHA Compliant Dust Collector Wars