Sorry, I must be really thick.

To drain a filled tank, do you not just remove the standpipe from the thru tank Bulkhead?
Is the stand pipe threaded into the bulkhead and the just unthreaded to remove for draining {emptying} or is the standpipe just pushed into the bulkhead? { without gluing?}
If the standpipe is glued into the bulkhead, how do you drain the tank?