Thread title says it all really - our waste tank is around 10 litres smaller than the waste tank, leading to additional and unnecessary water anxiety! Surely if the ratios were reversed, you could happily use all your fresh water in the knowledge that the waste wasn't going to overflow? As it is, we had a little 'accident' on our last site! I've not done a survey, but glancing at other van specs, this 'waste smaller than fresh' does seem to be common practice. Can anyone tell me why?