Hello, my mom just bought a house/cabin that has a kerosene tank outside, ive noticed on the tank where the pipe is attached it looks wet like a round 6 in damp spot and smells a little also the metal pipe with pvc around it looks greasy. She says she had a kerosine guy come check it out and he says its not leaking but on the tank itself the old owner drew chalk marks showing with dates measuring i guess how empty it was over the years one date being 1995 and another 1998. I read on here someone mentioning a “wet tank” can someone explain that to me and if its something to be concerned about also is it okay the tank is that old? Thank you