welcome to the forum its a great place to get your questions answered. Your question caused me to really wonder does it really matter? Not knowing your rig my answers are a guess based on general tank size on Rigs. There will be someone that will now the actual size.
Hot water 6 gal
potable water 30
Propane X number of bottles either 20 lb or 30 lb
Jake my sidekick (yellow Lab) 10/04 - 05/20
2017 RAM 2500 CC 4X4 Cummins Diesel
2016 Flagstaff 26 FKWS
AF&AM & El Korah Shrine of Idaho