I have 2 small cracks in my pool plaster with rust bleeding through both. They are about an inch or 2 below the bottom of the tiles.I noticed these after I removed the cover this year. The pool is about 13 years old but in great condition. I have a lifetime warranty on the pool shell which is gunite, but when I spoke to the contractor who built the pool he gave me every reason why the damage is not their fault and that I need to be prepared to pay for the repair after they do the investigation (destructive observation I suppose). Our experience with this contractor was not positive. I have no reason to believe they will be honest or fair. I need to know what causes this kind of damage. I have been told that when they tie the rebar together if the tie wire is not turned into the center of the wall it could poke through the gunite and bleed rust onto the plaster. This is clearly a workmanship issue but our contractor never mentioned this as a possibility. Can you respond providing what causes this to happen? Thanks for your help.