I recently changed my drain plug on hot water tank now there is only about 2-3 cups of hot water then it cold thinking tank my have air it it I open all valves ran water even drain fresh water tank st...
Just to be sure, you did shut off the electric while changing the drain, right? Many have said that the electric element has to remain under water or it burns out in a few seconds. Probably not the case since you do get a bit of hot water, but it would be a consideration while trouble shooting.