I was looking for the freshwater tank size on my 2011 16 QBB. Is it 30 or 38 gallon ? I ran out of water this long weekend. We were at a site that the shower house was quite a way from our site so we were using the water in the trailer to wash up at night and in the morning.
Most of the time we are near to washrooms that we can wash or brush your teeth in so we don't use as much water.
I found in the original sales brochure it says it is only 20 gallons. Usually it lasts my wife and I at least three to four days. If we are moving lots we can empty the grey and black tanks and fill water when we get to the new site. Also if we have access to washroom facilities to wash.
I looked but I don't think you could mount anything bigger. It is tucked between the frames. A bigger tank would not give enough ground clearance.