On passenger side, rear end, I see two blue (cold i suppose) and one red (hot i suppose) vertical drain tubes with turn type valves that look just like the valves at the bottom of the water feed to a household toilet tank. Obviously they are for draining something, however, I can’t find anywhere, including in the Owners Manual thumb drive provided with the trailer, a schematic that shows just which down-tubes drain which tanks and for what purposes and / or periodicity? Any / All tips much appreciated.