Vacuum truck

A vacuum truck or vacuum tanker is a type of tank truck that has a pump and a tank, designed to pneumatically suck liquids, sludges (such as fecal sludge), slurries or sand/water mixtures without the contact of any mechanical equipment. They are used to transport sanitary waste (human excreta mixed with water, e.g. from septic tanks) as well as for some industrial liquids or slurries. They can be equipped with a high pressure pump if they are used to clean out sewers from sand. 

Vacuum truck are used to transport the collected material to a treatment or disposal site, for example a sewage treatment plant.

Other names used for vacuum trucks: vacuum tanker, "Sucker truck" (in Australia) or "Sewer Sucker", "Hydro-vac" or "vac-trucks" (in Canada). Slang terms include: "honey truck", "honey sucker" (in India and South Africa), and "honeywagon", all (probably) derived from honey bucket.

When a vacuum truck is used to transport fecal sludge then it can also be called "fecal sludge truck".

Commercial vacuum trucks which collect fecal sludge usually have a volume of 10 - 55 cubic metres. However various smaller versions for specialized applications or low-resource settings can be found with tanks as small as 500 liters.

They generally use a low-volume sliding vane pump or a liquid ring pump to create a negative air pressure. The use of diaphragm mud pumps is less common, but with the advantage of a simpler design and usually lower overall costs. The disadvantage is that mechanical parts come into contact with the sludge, which is not the case for the more common vacuum pumps.

The truck can be configured to be a direct belt drive, or a hydraulic drive system.

There are two different ways to mount the pump: either directly on the truck with the vacuum drive powered by the truck motor, or on the trailer with an independent motor. The second option with the independent motor is more complicated and not commonly used. It has the advantage of potentially having the pump closer to the septic tank. It is also able to use the negative pressure suction side of the pump as well as the positive pressure side to pump sludge over longer distances or lift it higher into the tank.

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Wikipedia