How do i add nutes to a dwc

i was thinking changing the pure water out with pre-mixed nute solution?

wouldn't it be bad just to dump it into the res?

and shouldn't i change the water every few weeks anyway

I'm gona use cn17 grow/bloom (liquid)

i change my water every sunday no matter what...i also flush with clearex everytime as well....also as long as you mix the nutes the same way you can add more to top off the system if needed...i make my res 10 gallons bigger than the setup so you have 10 gallons extra throughout the week

thanks...another quickie, how do you kno when and how much to add? do you just add new nute solution every week or do you top off the nutes in between?