Any explanation (other than flood) for mold ring around basement water tank>\?

Hi all, looking to purchase a house and the basement water tank has what appears to be a mold ring around it. It looks as if the basement flooded at some point and left the ring but the seller told us there has never been a flood down there. Anyone have any idea what else could've caused this? See photo below.

That's not a flood as there's no line on the walls. It's from tank sweating due to cold water and dirt.

Mold is always caused by moisture and a substance it can breakdown "eat" likely dust or other organic material combined with sweating in the basement is causing this issue. The copper staining appears to be from condensation or a slow leak on the water line. I would assume condensation given the staining that has set in on the floor and the mold/mildew on the tank. If it is a water tank any time the temperature of the water drops below the dew point the potential for condensation can occur.

Mike Casey wrote:That's not a flood as there's no line on the walls. It's from tank sweating due to cold water and dirt.

Nailed it!

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