For the cleaning of sewer systems and deep boreholes in many cases suction operation is the only practicable method because:
- the lowering of a pressure pump with its driving-motor is rather difficult and expensive or,
- the cross-sections are too small for it, or
- solids carried in the water cause heavy pump wear.
The suction head however is limited by the atmospheric pressure so that theoretically water can be sucked up only from a maximum depth of about 10 m, and high-density mixtures only from smaller depths.
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