Dishwasher not draining completely

This was a piece of cake! Simply removed the rear drain cover with a nut driver and unscrewed the piston from its seat. I noted that the seal in the old piston had deteriorated over time. I rubbed a little petroleum jelly on the upper gasket of the new piston and simply screwed it into place, solving the problem entirely. Could not believe how quickly the part was delivered - next day!