Dan. I've got a similar valve. Mine turns but no water comes out. What did you end up doing?

Hi Ventana,
You piggybacked on a two year old thread. ( look in the upper left hand corner for the date,) so I moved you up to your own.
Gas or electric heater?
What has happened is that you've let your heater go for so long without flushing the sediment and mineral build out that it's built up and clogged the boiler drain. With a gas hot water heater this is costing you money. What do you want to do?
1) You can purchase and installn a new heater **OR**
2) You can remove the boiler and attempt to clear the heater yourself. Be aware that once the boiler drain's off and you're poking around with a wooden rod, (do not use a metal one) that once you get the threaded opening clear that will be 40 gallons of hot water attempting to drain out the opening so this could get messy. Do you wish specific instructions to do the job with instructions on maintaining your heater or will you be calling in a plumber? Let me know, Tom