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Flushing Duration RDWC


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Hey Guys and Gals,

Looking for some input on RDWC flush times. I understand some people don’t flush - awesome - but this post is for the people who do so they can offer input. I don’t want this post to get bogged down or turned into a debate about flushing, simply curious how long RDWC generally takes as I’ve read varying opinions.

So far I’ve run 6 hours of Flawless Finish, drained, and am now running pure RO water. Normally I’d go by yellowing leaves, but I’ve got to head out of town soon and need to make decision on running RO for 1 day vs. 3-4 days.

Wondering how many days typically suffice? Thank you!


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Think you’re left to my guidance and limited (although sound) wisdom here, Sativuhhh.

Understanding this is my first run at DWC/ RDWC - I can tell you with confidence 6 hours of Flawless Finish (or any other flushing agent) + 36 hours of pure RO water isn’t long enough. Take it til you start to see yellowing leaves. My guess is that’ll be 4-6 days, then chop WHOLE plant and hang.


Well-Known Member
Since this is your first DWC and I’m wrapping mine up, here some Informational Only takeaways that I had. May or may not prove valuable or useful to you, but sharing nonetheless. Lmk how the flush works out, I think you’re plant will do more than fine for 2 weeks. Wife said mine hasn’t even yellowed after 4 days. I’ll see tomorrow when I get home, but it’s coming down either way.

What I found:
-Figure out a way to ensure your shit doesn’t flood or lay things out in a way that’s eas(ier) to clean 5-10 gallons of water and nutes our of a tent. Seriously, think through this ahead of time.
-You don’t have to run DWC specific (mineral) nutes or have a super sterile/ pristine res. If you want ultra white roots, you do, but if you want more organic style weed you don’t.
-I saw best results with 64F water temp.
-If running with RO water, use EC as single source of the truth for feeding; I don’t think I’ll go above 1.6-1.8 max EC in future DWC grows. Also add calmag, but pretty sure you already know that.
-Use same water source throughout grow.
-Feed on the lighter side of what you think is needed, DWC is definitely different than coco.
-Change water at least every 20-30 days.
-Reduce feed under .6 in final week before flush.
-Start flush at least 6-7 days out from harvest moving forward.
-If you have a pH or deficiency issue mid run; drain res, flush out with flawless finish or a chelate based flush formula for a few hours, drain, then run RO water and add reduced feed back in. I’ll admit, I’m a hater of overpriced nutrients in a lot of cases, but with DWC a pure RO flush did not work even close to as well as when I used flawless finish to remove all buildup (you’ll know by EC measurements - this goes back to using EC as your single source of truth).

Good luck, send me a note when you start your journal and I’ll tag along.


Well-Known Member
Thanks for sharing your experience so far. I shall definitely be doing dry runs of processes and routines I'll need to go through and find the correct position for access. I'll be hanging light-proof material from the ceiling to the floor in the corner of a room where there's a vent to fix a fan over it, so I'll have more access points than from a tent. It' certainly seems more involved than soil growing. I'll let you know when I start a journal. I anticipate in a month or two.


Well-Known Member
It’s just different, a lot of upfront work. Key difference is you can really automate a lot and basically set the grow to cruise control once you’re dialed in. I’ll probably run a mix of coco and RDWC in the future, but need to redesign my setup to 100% eliminate any chance of floods.
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