water heater gone bad?
The year of manufacture is in the model #, unless it is very old.
If the tank has not been drained/flushed for a long time, the silt may be built up above the drain. A coat hanger or such can usually loosen the goop, but careful, that is hot water. If you only get hot water for a few minutes, sounds like the dip tube has deteriorated. It is under the cold inlet and is supposed to direct cold wat to the bottom while hot is drawn from the top. If the tube is shot, cold mixes directly with hot at the top diluting it. Dip tubes are not too hard to change(available at homes stores, plumbing supply), but if the tank is older than, say, 10 yrs I would not bother. Get a new tank.