I had a power cruiser and the manual specified bleach. 2 oz in the water tank (30 gal) and flush all lines. Stand for 3-4 hours and then flush very well with fresh water. As I recall, they also recommended a vinegar flush afterwards if there was residual bleach smell/taste. I have done this several times and not needed the vinegar.
First, the tanks need to be clean first. If there is sludge or anything on the walls, that means scrubbing with a long-handled brush and a hose. No chemical is going to penetrate the funk without some help, just like washing dishes.
Yup, bleach not vinegar. Dilute vinegar is not a sterilizing agent.
If you dislike bleach, hydrogen peroxide is a zero-residue way to neutralize bleach.
My preference is to clean and dry the tank in the fall. That way it is fresh in the spring. You wouldn't put dishes away dirty, would you?
