Due to the siphon hose always being submerged beneath the liquid surface, the air inside the feces tank is continually drawn out and, as it is not replenished, becomes increasingly thin, causing the tank's pressure to drop below atmospheric pressure. Consequently, the fecal fluid is then forced into the container due to atmospheric pressure. Alternatively, if the siphon hose is close to the bottom of the tank and air is continuously being pushed into the feces tank, it gets compressed due to having no outlet, leading to the tank's pressure being higher than atmospheric pressure. In this case, the fecal fluid is expelled from the tank under the force of the compressed air through the siphon hose and the siphon hose itself.

The vacuum cleaner trucks feature high suction efficiency, self-priming, self-draining, and direct pumping capabilities. The time to fill the feces tank is ≤5 minutes, and the suction range is ≥8 meters. They are known for their long service life, fast working speed, easy operation, and convenient transportation.