Draining hot water boiler

Houghta

Hi everyone,

we have just got our first motorhome (elddis autoquest 145 2012 model) so we are motorhome virgins so this might seem like a stupid question but can you tell me if we have to drain the hot water boiler every time drain the  fresh and  grey water at the end
of a trip and do I do this by opening the yellow handle beside the hot water boiler  cheers