Camp trailer water heater is dripping

My water heater was dripping at the drain plug when we bought the trailer, ours has a Dometic water heater so no anode rod. I pulled the plug and saw that the threads in the water heater tank were stripped out so I ordered a 1/2" 14  NPT tap and chased the threads in the tank twice.

And then put a new plastic plug and teflon tape in it and it still leaked. So I had already ordered a brass drain valve and I pulled the plastic plug and put a lot of thread sealant on the brass drain plug and installed it and let it set and no more leak. Now before you say the brass plug may cause corrosion in the tank remember it already has a brass pop off valve in there already.