Drainage Question

Looking to start my first hydroponic grow and have been watching a lot of videos of various set-ups and techniques. I've started planning and understand how hydroponics work, but I've run into a little problem that the videos have failed to answer, so I've turned here.

In every one of these videos the grower has the plants draining back into the original basin/reservoir with the nutrient solution and the pump that supplies it to the plants. In my previous soil-growing experience, I've had a single reservoir that I mixed and distributed, constantly refreshing with new water and nutrients. With the drainage returning back into my reservoir in a hydroponic grow, do I need to re-treat my solution? It doesn't seem "clean" to have old water and chemicals cycling through. I understand I can refresh with new water, but how do I know the strength of my solution and how much new nutrients do I add? Or maybe I need a second basin just for runoff?

Hope I'm clear and thanks in advance.

What you are talk about is a drain to waste system...I hope this helps

It will be clean for a few days then will need to be treated to avoid bacteria and the like forming in your reservoir.

Treatment of the water with hydrogen peroxide and then readjusting the fertiliser and PH levels will bring you back in business.

I look for symptoms before changing my reservoir whilst many gardeners will change it routinely every 2-3 days. I still monitor all my res. variables daily.

bulletproof system in my experience.