An apparatus and method prevent entrained solids from entering a pump by directing a process stream through an active upstream filter that removes the solids, and then through a downstream idle filter where the process stream purges the filter of previously retained solids. The flow path is periodically switched to exchange the roles of the filters, so that none of the filters is saturated, and the solids remain in the process flow but bypass the pump. Any need for a low pressure destination for purged solids and purging fluid and/or any environmental impact of dumping process fluid and solids into the environment is thereby avoided. Partially opened valves can be used to divert only part of the downstream flow for filter purging. Selectable paths can be included for which no filters are purged. The downstream flow can be divided and used to simultaneously purge a plurality of idle filters.