Vacuum trucks are vehicles that typically consist of a storage container and suction motor mounted on a truck chassis. These vehicles can be used to pump anything from residential septic tanks to contaminated soil. Vacuum trucks are sometimes classified based on whether they are designed to pump wet or dry materials, capacity, weight, and other factors. The vacuum motor can be powered by the truck engine or a dedicated gasoline or diesel motor. A vacuum truck is usually purpose-built on a heavy duty chassis, though slide-in units exist that can be installed in a truck bed or on a trailer.
Any time a substance that is loose enough to be pumped has to be removed, a vacuum truck may be used. The material can be sewage from a septic tank or sewer, contaminated soil from a jobsite, brine water from an oil well drill site, or virtually anything else. Liquids typically require different vacuum trucks than solids, since a pump designed to work with liquids may not function well with substances that are more solid in nature. The pumping tubes used with vacuum trucks are typically between one and four inches (2.5 to 10 centimeters) in diameter, though this can also vary depending on the particular job.
The pump on a vacuum truck may be operated by a power take-off (PTO) from the vehicle's engine or a dedicated motor. A power take-off is usually a splined drive shaft that is connected to the drive train of the vehicle. When the truck is stationary, power can be cut off from the wheels and transferred to the power take-off instead. This drive shaft can then power a variety of different items, such as the pump on a vacuum truck. The PTO on a vacuum truck may use a belt to drive the pump, though hydraulics are sometimes used as well.
If the vacuum unit is mounted on a trailer or in the bed of a pickup truck, it may not be feasible to use a PTO. In situations such as these, a small gasoline motor is often used to run the vacuum pump instead. This is sometimes called a pony motor, which is a term that can also refer to small gas motors that are used to start larger diesel engines.
To facilitate pumping, a vacuum truck is typically equipped with some type of boom. The pump tube is fastened to this boom, which can make it easier to position it over the material that has to be suctioned out. This is often helpful when vacuuming out a septic tank in a back yard or a drill site where equipment or debris prevent the truck from approaching closely.