Originally Posted by Paul R. Haller
I'm guessing you have a sulfer smell from the hot water side of a faucet or shower? If yes, sanitizing will not help. What you are smelling is the sacrificial anode in the hot water tank and it's breaking down to prevent electrolosis.
-Paul R. Haller-
The sulfur smell can also be the result of bacteria that release hydrogen sulfide (rotten egg odor) as a metabolic byproduct. These bacteria do tend to reside in the hot water tank or hot water lines. They are harmless and typically come from untreated well water.
Sanitize your water system with household bleach (.05% sodium hypochlorite) at 1 oz per 10 gallons of fresh water. The "kill" with sodium hypochlorite is pretty much instantaneous unless you are dealing with a biofilm (unlikely) so fill your fresh water tank, add the bleach, run the sanitized water through all the taps until you smell slightly bleachy, let it sit for 10 minutes, drain and rinse.
It will not do a better job if left longer, so why bother? It won't hurt either, unless you are really overdoing the bleach.