A problem with dishwashers of the above mentioned type is that the filter has a tendency to clog by soil particles that are caught at the filter. Therefore, conventional dishwashers are normally equipped with two filters, i.e. a fine-mesh filter and a coarse-mesh filter. The circulation flow is then divided between the two filters, wherein most of the flow passes through the coarse-mesh filter and the rest of the flow passes through the fine-mesh filter. Thereby, the major part of the larger soil particles will be caught at the coarse-mesh filter. The finer particles will only be caught at the fine-mesh filter, some instantly and some after passing through the coarse-mesh filter and passing through recirculation. Thus, this arrangement reduces the load on the fine-mesh filter.
However, also in these types of conventional dishwashers the filter might clog during the dishwashing. To achieve a desired washing result, the filter may need to be cleaned, which is cumbersome for the user.
Dishwashers equipped with a filter cleaning function have previously been designed. One example of filter cleaning is flushing of water through the filter in a direction opposite to the circulation direction. Filter clogging could however still be a problem.