Which unit uses high water pressure and a vacuum to clean sewer lines?

The combination unit is designed to clean sewer lines using both high water pressure and vacuum suction. This dual functionality allows it to effectively remove blockages and debris from sewer systems. The high-pressure water helps to dislodge and clear obstructions from the pipes, while the vacuum system simultaneously removes the dislodged materials, ensuring a thorough cleaning process.

Other tools mentioned, such as the jetter and mechanical rodder, typically focus on either high-pressure water cleaning or mechanical removal techniques, and do not provide the vacuum capability that is characteristic of a combination unit. The bucket machine is generally used for different purposes related to excavation or lifting, and does not perform the specific function of cleaning sewer lines in the same comprehensive manner as a combination unit does. Thus, the combination unit stands out as the correct choice due to its integrated approach to sewer line maintenance.