+1
If you have pythia, protozoa, parasites, or "bad" bacteria you should definitely flush your system.
Heres how.
1. empty the rez and drain all liquid from the system.
2. clean the rez tank, pods, hoses, spray bars, pumps, pots, and anything else that is part of your hydro setup.
3. use something to sanitize the parts of the system that can be completely removed from the plants. I.E. the rez, hoses, pumps, etc... I use bleach, I know that some will have issue with this, It's what I use and it works for me.
4. rinse everything
5. rinse everything again
6. put the system back and fill the rez with plain water. NO nutes.
7. Add H2O2 to the water, the recommended amount is 1 tbs. per gallon. I have used a bit more than recommended at times. I've also seen weird shit happen when using H202. you can use chlorox or some other type of oxidizing disinfectant as long as it is plant safe. As fatman stated.
8. run the system for 30 min. to whatever you feel is necessary. Make your system run on a constant loop. I.E if you use a drip make the drip run constantly for the duration. Or if you use spray bars make the pumps continue pumping for the duration. Or is you use ebb and flow make the pods fill and drain constantly for the duration.
9. Drain the rez.
10. repeat steps 3-6. You may elect to only clean the rez at this point, but I would at the very least clean and sanitize the rez.
11. put the system back together, fill the rez with water, and add your nutes.
Back up a bit Ivan. YOU DO NOT HAVE TO DRAIN THE RESERVOIR AND ADD FRESH WATER WITH CHLORINE IN ORDER TO DISINFECT YOUR SYSTEM OR TO KILL PATHOGENS. Just add the chlorine to a concentration of around 2.5 ppm to your already in use nutrient water. Run it for a few hours and drain. Wipe out the reservoir well with a 1 to 10 (chlorox to water) solution of chlorox. Fill reservoir with new water and mix as usual and pH balance and restart system. Add enough chlorox to obtain a 0.5 ppm concentration.
As a matter of fact if it was not for needing to remove all the dead partially decomposed organic matter and the bacterial biomass that would just later feed other bacteria there wouldn't even be a need to drain the reservoir and the chlorox.
After you do dump your reservoir and wipe it outs and replace the water and nutrients you should continue with maintaining a low level of chlorine, 0.5 ppm, in the water untill you get the root rot in check or until a few days before harvesting the plants. This means if your reservoir is aerated or your growing using sprayers etc then add a dose of chlorine day at an amount equal to adding 0.5 ppm per day.
If the systems is already badly caught up in root rot then when you change your reservoir out after the first dose of chlorox again to dose to 2.0 ppm instead of just 0.5 ppm. From there continue with 0.5 ppm per day.
If it's protozoa or parasites (fruit fly larva) just use azatrol. It works great, it's derived from nature, and it has a half life of less than three days. It may turn your rez a milky color at first. Don't panic the milky color is normal and should subside over time in my experience.
Burning Buhach works real well fir mtyes, flys etc. It is a pwder that you light with a match and it just smolders andproduces a smaoke. The smoke gets into every nook and cranny. Some do not like the smell but it is harmless. It is used for mosquito control in rural homes through out the U.S. It is a must in Alaska where some call the mosquito the state bird.
I can see no good reason to flush hydro systems for an extended period of time. 3 hours would be my max flush for any hydro setup.
Only 2 reasons come to mind.
1.I would for that long would be because the system has a prolonged cycle time. i.e. some ebb systems take a long time to fill the pods and then recycle the water back to the rez.
2. I would flush a system for an extended period of time that was infested to the extreme. In this case I may even flush the system more than once.