[ljcoren]

Diswasher is leaking from bottom. I can see water coming down the large tube that goes up to the center spray arm. I'm thinking there must be a seal in the bottom of the diswasher but I don't know how to get to it. Could there be another reason for the leak? It only leaks when the washer is running I don't see water coming down when it is filling.

[denman]

Here is the parts breakdown
Replacement parts for General Electric GSD4020Z05BB Dishwasher | AppliancePartsPros.com

The spray arm assembly screws into the pump connect (Item 455 in Section 3).
This pulls the pump connect up to make a seal with the bottom of the tub.

I think the first thing I would do is try to see exactly where the leak is.
Could be at the seal or the pump connect may be cracked or the water may be spraying up and then dripping down.

A flashlight and a small mirror are helpful here.
A mirror on a long handle, like the ones mechanics use, is best as it is not a good idea yo have your hands under the unit when running it. You could also tape a small mirror to a dowel.

[ljcoren]

Thanks for the help, it turns out it is leaking where the motor shaft goes into the pump housing. I need the impeller and seal kit which I will order.