Prime pump through discharge outlet for start up at any water level; Internal check valve holds prime and prohibits back flow through pump when stopped; Urethane, Semi Vortex Impeller and Wear Plates for maximum durability and maintaining pump performance; Dual Inside Mechanical Seal With SiC faces provides longer operational life; Oil Lifter provides lubrication of the seal faces; V-Ring Seal design protects mechanical seal from abrasive particles