Fresh Water Tank Question

We just purchased a brand new 2018 Carbon 387 toy hauler, and recently took it in for a bevvy of minor warranty issues. The only issue our servicing dealer could not address was the fact that we have to have ~30 gallons of fresh water in the tank for the water pump to function. The technician found the same issue and stated it is "as designed". Really??? Does anyone else have an RV fresh water system that requires you to maintain more than 25% of it's rated capacity in order to function? I mean heck, that means I get the pleasure of hauling around 30 gallons of water, and the 240lbs it weighs, without being able to access it?! Unfortunately Keystone is closed for the Thanksgiving weekend already so I sent them an e-mail, but wanted to get some feedback from the rest of the RV world? There is simply no way this can be "as designed"????