In large profiles (> DN 1,200 (48 in)), the method of high pressure cleaning that is most frequently used in drains and sewers often reaches its limits. This is, because the distance between the cleaning nozzle and the sewer wall becomes too large, minimizing the cleaning effect of water jets. Owing to the structural condition, for example, of the invert area of sewers made of brickwork, an increase of the maximum flushing pressure is often not possible. The only possibility to increase the energy input is an increase in the flushing water volume. However, in large profiles with a high partial filling level, all that is required to transport loosened deposits is to increase the  velocity of the already high volume of wastewater. In this case, high-capacity cleaning vehicles with at least two pumps (640 to 800 l/min) or ejector nozzles are to be used.

For maintenance cleaning, the continuous surge- or back-up flushing can alternatively be applied, as long as the structural (e.g. accessibility) and hydraulic (back-up level, quantity of flow available) conditions are appropriate for the purposed solution.

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