Bleach not damaging when used as directed
While bleach (chlorine) IS corrosive, it’s effects are are cumulative...and it's the cumulative effect of carrying chlorinated municipal water for years that does the damage to metal tanks...Which, btw, makes it a VERY bad idea to add a little bleach to each fill. Not only does it damage the system, but unless you add enough to make your water taste and smell like a laundry, it’s not enough to do any good. Even if it were, any “purifying” properties in chlorine evaporate within 24 hours, leaving behind only the corrosive properties. If the bleach solution used to recommission the system were allowed to remain in the system, it would be highly damaging...but the directions call for completely flushing it out within 24 hours, which does no damage at all. Nevertheless, it's a good idea to mix the total amount of bleach in a few gallons of water before putting it into either a stainless or aluminum tank. Btw, Patrick...why go with fiberglass--which can have its own set of problems--blisters, moisture absorption that leads to rot, etc, and a lot more weight...why not go with a good quality polyethyelene tank? If Ronco Plastics doesn't have one that'll fit among their 400 shapes and sizes, you could have a welded tank poly tank made. A good quality poly tank will last as long as the boat itself.