Most water heaters do not have bottom drains. What leads you to believe that 2 of those tubes are bottom drains for the water heater ??
Most likely, the 3 tubes are for your water lines (blue-cold water, red-hot water), and the 3rd tube would be the fresh water tank. Check out the vicinity of the fresh water tank fill, see which way the fill tube heads, and most likely the fresh water tank is in that area.
BTW, welcome to the forum !!!
Chap , DW Joy, and Fur Baby Sango
2006 Ford F150 Super Cab 4x4
2008 Surveyor 263