Help in changing from caravan to motorhome

Fresh water tanks have to comply with EU Regulation EN1646-2 issued in 2008 which defined, for health & safety purposes, Mass in Running Order as including basic equipment (75kgs for driver, filled fuel tank, water tank in driving
condition filled with 20 litres). For c £130 you can get a copy of the standard.

If memory serves me correct, manufacturers can either put in a 20l limiter as Hymer have done on its motorhomes [the limit can be overridden] and recommend to people that is the recommended safe limit or tell people not to put
in any water when driving.