Question about Watering Regiment

ok so i am fairly new at growing and i recently switched to hydro to try it out and i was wondering how people water exactly? such as at each watering do you dump out the rest of the old water then add fresh nute water? or just add the fresh nute water to the old nute water? i buy gallon jugs of water and add the nutes to them...for me when i fill up my resivor should i just add the gallons of nute water or gallon of nute water with one or two gallons with just pure water to mix it? any input would be appreciated and for the dickheads (there is always one) dont come on here talking shit....just in advance

I will add a little h20 during the week to keep the levels up and compensate for evaporation. then about once a week, depending on how much they are eating, i completely pump out my rez and mix up a fresh batch. this keeps the salts build up down. i also flush once a week.

ok thanks man thats what i have been doing except the flush once a week, since i was adding strait water throughout the week i figured it diluted the nutes enough so the nute level is low and they are drinking mostly clean water with some nutes towards the end of me dumping the remaining water

what are you growing in?

its like a 6 gallon tub with 2 net pots with an air-rator or w,e its called, nothing fancy i am a broke college kid