A reductant insertion assembly includes: a first pump configured to pump a predetermined amount of a reductant into a selective catalytic reduction system; a reductant delivery line configured to deliver the reductant to the first pump from a reductant storage tank; a reductant return line configured to return reductant to the reductant storage tank from the first pump; a second pump configured to pump the reductant from the reductant storage tank to the first pump; and a valve selectively moveable between a closed position in which the second pump pumps the reductant through the reductant delivery line to the first pump, and an open position in which the second pump draws air through the valve and pumps the air through at least a portion of the reductant delivery line downstream of the valve and the first pump to purge the reductant insertion assembly of the reductant.