With the eight dollar socket and breaker bar handle specifically designed to fit, it unscrews good.
Best to just quick stick a rubber cork stopper, about 1 1/2" diameter into the hole, then go to local hdwe store for replacement.
Draining the tank to do this is a big messy waste of time. Just plug it and run to hdwe.
You knows, I can do this with one hand tied behind my back while blind folded, and I'm about as smart as a moose with the brain worm disease! ....

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Just compare a new in-the-package element diameter, all the same, to the big rubber cork stopper, at the hdwe store, to get the correct size stopper, which is key to a no-leak rubber stopper. U gotta get the correct size stopper.