You may have several types of tanks like those that fill water and those that fill liquids other than water. For those tanks that store liquids it is possible that some problem is likely to occur because of the chemical reactions of the liquids that are stored in the tank. Though you could not stop the reaction of chemicals you could at least reduce the extent to which the reaction is likely to occur. How about using the repair putty that has all the good features like having excellent strength, bonding and resistance against chemicals.
After knowing these features it is no wonder that you would start keeping it handy for use in various locations.