Ben wrote:I'm going for a 30-40 gal water tank, an ac unit with a large tongue box and a full galley the 2500 lbs was just a high weight but I do know that my frame is heavy with it being 2x3x.120 wall tube I used 3 sticks 24ft long and the tongue is 3x3x.120 wall about 10ft long and I also have more to add to it for the water tank supports.
The overall size is 5' 4" x 10' x 4'
Let's see. Water weighs 8.34 pounds per gallon, so 30-40 gallons would be 250 to 335 pounds. With the 3/4-inch plywood and huge oak framing, I don't think you would need any extra support even with tanks this large.
Another comparison: our 25-foot Airstream has a 37 gallon water tank that we seldom use to capacity because water is plentiful in most campgrounds. I should think it preferable to have a smaller tank that you drain completely frequently rather than carry around stagnant water for days and days at a time.
Are you planning to have a shower or bathtub too? Otherwise, it's hard to imagine a need for so much water storage. That's also 4 to 5.3 cubic feet for the tank. At 5.3 cubic feet, you're looking at a tank the full width of your trailer that's also 1-foot high and 1-foot wide. You might want to baffle such a big tank.