I think it’s useful to you “Shut off supply valve and unscrew (remove) the drain valve completely. Have a large bucket or other way of catching the water and junk that will flow. This method is ideal if your heater is located in an area where the resulting flow of water won’t do any damage. One work of caution; some of those cheap plastic valves will break if not careful.” You can get all the information about plumbing here
