Sulfur smell

Sounds like you have sulfated water which is caused by sulfur in the water SOURCE. This is sometimes also referred to as "onion water". If you always fill from a municipal water system that does not contain a lot of sulfur you SHOULD not get Sulfated water. If you DO end up with the problem, all it takes is to drain, flush and sanitize your water system to get rid of it. Of course after sanitizing you'd still need some more flushing to get rid of the bleach odor and taste.

It doesn't have anything to do with anode rod or length of time the water is left in the system, it's in the water SOURCE and builds up over time.