i normally do 30 % run off if i use 11 liter pots but with these 80 liter tubs you dont really get run off unless you really soak them if i do that i get 10 % run off .
iam hand watering ,but i do use a pump sometimes i attach a hose to it .it works well ...as for my run off my bench has a slight angle to it so all the run off runs down the corrugated sheets in to my guttering and into my tub which has a float switch in it and a pump so it just pumps my run off to a barrel .check the pic