I have a fire tube boiler with one tube leaking. Boiler inspector noticed.The boilers are over 30 yrs old and are going to be replaced next year.I have a concern with plugging. If water enters the tube and the leak seals, the water could steam in that tube. Steam pressure could cause major failure. It is hot water and not steam. Typically the water is 180 deg. Should be no steam.I am going to site tomorrow to evaluate.