Putting water into the fresh water tank
We have a 32 foot RKDS Sabre TT that according to 2 spec sheets has a 42 gallon fresh water tank. When I add water, I add it until it runs out of the fill spout. I then drain the tank until nothing comes out and only get out approximately 13 gallons. Since the bottom is covered, you can not see the tank or any of its components.
Any ideas on why I can't get 42 gallons in the fresh water tank? It seems like only approx 13 gallons is going in as well. Please help.