Low Point Drains

I began winterizing my 5th wheel and I can't find the low point drains. I have one drain underneath with a valve that empties the Potable Water tank. I have a Potable water tank overflow tube underneath on the passenger side with a sticker that says Low Point Drain but no shut off valve. I know this is the Potable overflow tube because I've overfilled the Potable tank and that's the tube the water comes out. I have another overflow tube next to the Potable Water drain and I don't know what it's for. Nothing has ever come out of that tube. Probably Gray tank but not sure. Neither overflow tubes have valves. No other drains are under the camper. Any ideas where the low point Hot and Cold drains would be?