don't run to waste .. i did it for years and it's uneccessary .. plus it can bring you more problems than anything .. because you will always do the smaller runoff possible .. and it will lead to salt accumulations
it's fine to recirculate, if you work fine you dont have to dump your res .. same res from start to finish
be sure to use water containing a bit of disinfinctant agent .. to keep it pathogens free (ex: water from the tap containing a bit of chlorine, or condensate/RO water with a low dose of h2o2 )
ideally you dont want to use substrate like coco .. because they decompose with time and then the npk ratio of your solution will slowly change, rockwool is the best for this
a reservoir kept out of the room (far from fan/air circulation) without air pump mixing it will allow you to keep the h2o2/chlorine in your solution without adding some every day)
if you want to push the thing farther, with sealed room condensate water from AC /dehumidifier are all recovered in a second reservoir out of the room. you also recover the runoff of your room inside this reservoir
you just need to add a dose of h2o2 before pouring it inside the main reservoir, then a pump will suck it and send it through the irrigation line/drip emitters through your plants
with this method you never use any water from the tap .. never
plants use less than 5% of the water you give them .. all the remaining water is transpired and recaptured by the AC/ dehumidifiers.. the co2 burner of the room is also giving some more water in the air
for your nutrient lockout problem, the key is to give a big runoff everytime.. the problem of ebb/flood method is that it have tendancy to lead to salt accumulation, because flooding from the bottom without top feeding push the salts to the top ..
the best are hybrid systems .. with ebb flood and a line of drippers at the top
never get any salt buildup this way .. thats how the professional dutch growers do it .. with mapito ( rockwool)