A reductant storage system for an internal combustion engine system includes a storage container having a bottom wall, a top wall opposite the bottom wall, an opening extending through the top wall, and a reservoir formed by a hollow interior of the storage container; a filter assembly; and a header assembly. The filter assembly extends through the opening and is configured to seal the opening and includes a filtering material. The header assembly extends through the opening and inside the filter assembly. The header assembly includes: (i) a first sensor configured to measure a quality of the reductant contained within the filter assembly and (ii) a second sensor configured to measure a level of the reductant contained within the filter assembly.