I have my dishwasher all apart, looking for why it isn't draining completely. I plan to replace both check valves. Otherwise everything inside looks reasonably clean and clear. My question is: there are a couple of places where hard plastic joints slip together, such as where the sump spout goes down to the drain pump. When I put it back together, should I use any kind of sealant on joints like that, or will they press fit tight enough without it?

All I'm asking is, should I use some sort of sealant on places like where the tube from the top part slips into the tube sticking up from the sump? What about the housing that goes over the chopper assembly that you have to remove to get to the check valve; does it need a sealant?