Me: It's the one that is connected to the main wash pump
E: Which motor is that?
Me: The 45kw one. (read "The only motor in the pump house")
E: Ah... The tanks aren't conected yet.
Me: Then the header tank will be the tank closest to the main wash pump.
E: Which one is that?
Who here is an engineer I can *headslap*? You will have to represent all the engineers I am talking to. Nothing personal, I just need an engineer.