Why the outlet? Wouldn't the H2O2 (or bleach) only treat the upper stratum of the water? Injecting it via the inlet, it starts out at the bottom, close to all the accumulated crud where the bacteria live, and rises with water flow and convective currents.
A sufficient amount of H2O2 added to the OUTLET of a water heater and allowed to sit there overnight is much safer than turning up the heat. If you first flush off the bottom for several minutes, you will remove some of sediment that the bacteria can thrive in. This will solve the rotten egg odor 95% of the time and you won't void the water heater warranty by removing the anode rod (which rarely works). Hydrogen peroxide kills faster than bleach and when it breaks down, the second oxygen molecule comes off becoming water.
Disinfecting the outlet only is a really bad idea and draining the heater and flushing it leave more than enough sediment in the tank to prevent any benefit from doing it because the drain valve is on the side of the tank a couple inches above the bottom of the tank but, IRB lives on the inside of the heater and especially on the anode rod.
If needed I can tell you how to prevent burns if you want to use heat to kill the bacteria.
Gary Slusser Retired (= out of business)
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