A reference electrode system for a pH-sensor system includes: a first junction having a membrane with a sealed side; a reference electrode, the reference electrode and/or an electrically conducting wire of the reference electrode being covered completely except for an end portion of the reference electrode, by a sleeve; and a tube that is arranged, at least partly, around the reference electrode, the electrically conducting wire, and the sleeve, the tube having a closed end which is arranged near the end portion of the reference electrode.