Reason #2 why I switched to the dry method for winterizing.
Do a full sanitize, Bleach (1/4 cup to 15 gallons) fill tank run pump flush through lines till you smell bleach, do not forget showers and toilet and do not forget low point drains
Drain
Optional fill with fresh and flush till bleach goes away. Drain
Refill with fresh water and some baking soda, My tank is 70 gallons I use around 1/4 to 1/2 pound.
Flush and drain
Optional refill with fresh flush and drain
Refill with fresh and taste.
Come winter Use dry method described in forum library.