Your furnace is not being drained. Condensation forms in your exhaust as your furnace runs. It can create a LOT of water. I have seen this problem before on these models. When the inducer (ventor) motor kicks on it sounds like it's sloshing with water right?
There should be TWO drain hoses fitted to your furnace inside the upper cabinet.
In this pic,
you can see the 1/2 inch black plug at the bottom corner of the collector box. There should be a hose (supplied with the furnace) to drain this to a drain box that is affixed to the outside of the furnace opposite the filter rack. There are two like plug on either side of the collector box depending where you had the furnace cut out for the return air. (IE it can drain from either BUT not both)
In this pic,
you can see where the second hose MUST be attached. That 2" long beige nipple hanging down should be cut (only about cut off 1/2") and another hose with clamps (again supplied with the furnace) attached and connected to the drain tubes that go into the drain box. OH and have a small bucket or can handy to catch all the water that will pour out of that nipple. Best to not have that go down to the control board.
In your pic of your entire furnace I didn't see a collector box on either side as it appears you have your R/A coming in underneath so you can place the drain box on either side it doesn't matter. There should have been included with your furnace a bag containing a drain box with 3 green clamps, 1 red clamp, and 1 grey clamp along with one 45 degree male/male connector for that beige nipple. There should also be a short ~6" hose in a slight J shape and a long ~18" hose ending with a slight J. It would be easier to drain on your left (furnace right) opposite the wiring as you have more room to work.
If you cannot locate this bag opened the lower cabinet and check under the blower motor sometimes it gets pushed back there and forgotten. If it's no where contact Goodman for replacement parts.