can someone explain hydro res flushing to me? (how to?, how long?, plain water?, etc...)
Res-flushing is the process of removing built-up salts from your res. Most nutrients used in hydro are made from dissolved fertilizer salts, and these salts can build up.
No nutrient solution (that I know of) is "perfect" for all stages of MJ growth. MJ will use differing amounts of a particular nutrient (like nitrogen, for example) throughout the grow. If the plant is using less of a particular nutrient then is being supplied, then as water is used that nutrient will build up in the res in the form of a salt. Have you ever dissolved table salt in a glass of water and watched salt crystals form as the water evaporated? Same principle.
Why flush: If you allow these nutrient salts to build up too much you can start having toxicity or lockout issues. So you periodically flush your reservoir and roots with
ph-adjusted plain water. You can also add a supplement like Clearex to your flush water.
When to flush: Many people flush with each res change; I flush twice: once when I switch from veg to bloom nutes and a final flush for 1-2 weeks prior to harvest. And as Illegal Smile says, flush when you have a problem with your plant that might be related to nutrients or water quality.
How to flush: fill your reservoir up with ph-adjusted water or a Clearex solution and run the system with the plants in it.
How long to flush: If I'm doing my mid-grow flush or a problem flush then I'll monitor the ppm level of my flush water. Once the ppm level stops rising then I'm done flushing and I'll change the res back to nutes. Typically takes about a day for me.
If you're using Clearex follow the instructions on the bottle. If it's the end of grow flush then I'll run the system on plain water for 1-2 weeks, 2-3 res changes with plain water along the way.
Hope this helps...