slow drip from insulation around low point drains

Folks, I was blowing out the lines with a shop vac ( i had hot and cold Fawcett taps on inside in the kitchen sink), collecting water from the fresh water tank drain and noticed a small drip coming from the insulation (foam) around the low point drains. There's no way to see whats happening because it's all enclosed. Another question too, why is there two low point drains (hot and cold?).