If you check the drain plug on the bottom if the stock number is 86202000 Drain Cap Assy. Then it's the standard 1.5 inch PVC plumbing thread stuff. I used an threaded 1.5 inch to PVC then a section of pvc an 1.5 inch ball valve and then out to the driveway to drain.
The drain cap assy is like $10 and a 1.5 inch threaded cap is only $.89 and does the same thing, go figure.