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A shop vac or wet and dry vac is a great tool to have in the garage or on the jobsite to remove dust, dirt, and wet grime of all kinds. Shop vacs are useful in wet or dry situations, which means their uses are practically endless. If you’re looking for a shop vac, there are a few specs to consider before choosing.

What should you look for in a capable shop vac?


The maximum power output of the motor is called peak power. Although peak horsepower is often posted with each shop vac, you shouldn’t get too caught up in horsepower ratings. They may not indicate the actual operating power you will use when cleaning and may not be a valid point of comparison.

sealed pressure

Also, it’s not a very comparative spec, useful suction pressure is measured without airflow, and airflow makes up a large part of a vacuum’s performance.

Cubic feet per minute (CFM)

CFM is a valid point of comparison. It represents how much air the motor moves or a specific system load. If all other specifications are the same, such as hose type, size and length, accessory tool being used, and a clean filter, you want to get the most CFM for your money. CFM is especially important when collecting dry masses.

sealed suction

Airflow measures CFM (cubic feet per minute) or volume of air moved, which is important when collecting dry mass. Sealed Suction (Inches) measures the raw force of suction when picking up liquids. If you plan to use your new wet/dry vac for mostly dry dirt, then a higher CFM is desirable, while if you’ll be using it for more wet dirt, sealed suction is more important. If you want the best of both worlds, the higher number for both would be ideal.

air watts

A newer term used by manufacturers of central vacuums and other types of machines to classify each model is air watts. While most agree that it’s not as useful as a comparison tool, the Air Watts captures both aspects of suction, including sealed suction and CFM.


Make sure you get the right size vacuum for your needs. If you are going to regularly vacuum up substantial amounts of water in a flooded basement, you should get the largest capacity that makes sense for your budget. On the other hand, if you clean small masses around the house, car, garage, or shop, then you should be able to get away with a smaller capacity.

Remember that the published gallon figure refers to the volume of the drum and not to the total collection capacity. The capacity of any wet/dry vac depends on the type of debris you’re collecting and how clean the filter is, among other factors.

There is no doubt that a wet dry vacuum cleaner is an essential tool in the workshop or garage. Buying the right shop vac for your needs means comparing apples to apples when it comes to specs. Understanding shop vac specifications is important in choosing the right wet/dry vac for your needs.

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