What to Look for in a Vacuum
When choosing a vacuum, don’t be distracted by its horsepower—this is purely a marketing gimmick. This number is not based on the operating current of the vacuum, but rather on the in-rush current when it’s first turned on. A vacuum that’s truly four horsepower, for example, would produce so much wattage that it would probably blow the circuit breaker in your home. Instead of horsepower, consider the vacuum’s airflow and suction abilities.
Airflow. Airflow is measured in cubic feet per minute (CFM) and refers to the volume of air that the motor can inhale and exhaust in one minute. For dry soil, airflow is the greatest indicator of a vacuum’s performance. High-efficiency vacuums meant for dry soil can move as much as 156 CFM, and liquid-focused vacuums will be around 88 CFM.
Suction. If you want a vacuum designed to remove liquid, focus on its suction. This attribute is measured in inches and refers to how high a motor can lift a one-inch-diameter column of water inside a tube. A vacuum specifically designed for liquid removal might have a suction rating of 150 inches, while one designed for dry soil will probably be around 12 inches. Due to technological limitations, vacuums cannot be extremely effective with both airflow and suction.