Dan123
I have exactly the same problem and wish that I knew the answer. If I turn the large nut, the whole hose twists. If I continue to turn it, it eventually will come right out of the heater and water everywhere. There must be a better way!

Looking for a solution.

It is not a regular "valve". This plastic drain valve has 2 sets of threads. First, drain heater. Then you grab the larger white nut and unscrew it all the way. Than it will feel loose inside the heater but still won't come out. Here, you pull on it towards you engaging the second set of threads. You have to keep unscrewing, until the think comes out...

First set of threads operates the OPEN / CLOSE function of the drain valve. The second set of threads actually UNSCREWS the valve nipple itself.

Important: The second set of threads is usually Counter-Clock-Wise. That's because when you operate the drain valve so you don't accidentally unscrew the entire nipple from the tank.

It is a good idea to replace this flimsy plastic "valve" with brass garden hose valve.

Good luck... Let me know how you did ! Milo

Thanks so much Milo. I'll give it a try. I won't be able to do it until next spring, since I did get it drained with a mess, and left it empty until I return next spring.
Regards, PCO

Milo gave you excellent advice.
Let me flesh it out a bit. First purchase a brass boiler drain,(see image) from any plumbing store. To install the new valve turn the power off to the heater and close the cold water supply. Now open the nearest hot water faucet to prevent air lock and drain the tank. Follow Milos instructions to remove the old boiler drain.
Wrap the threads with 3 wraps of Teflon Tape and screw the new valve in the tank.
Leaving the hot water faucet open fill the tank until water comes out of the faucet.
Shut the faucet off, turn on the power and in a short time enjoy hot water. Good luck, Tom

Thanks Tom, I appreciate the step-by-step, and the recommendation to install a brass boiler drain. I intend to do so at the time we return to our place in Alaska next spring. A simple thing, after all the hassle of figuring out the problem presented. Especially when I was winterizing the place and trying to drain the tank and blow my water lines to catch a plane. Don't want that hassle again next year. Thanks again, Paul