DTW, but re-using some of the runoff?

  • Thread starter phxazcraig
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phxazcraig

phxazcraig

543
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I've been running a DTW system for 4 plants in coco coir, and things have gone so well the biggest issue is my plants being too tall.

To get there, I've been running a lot of fertigations, currently up to 7x daily, with one of those in the middle of the night and the rest under lighting. I've been fighting a rise in runoff EC throughout the flowering stage, and that has resulted at times in tremendous amounts of runoff.

Until I just swapped out my 14 gallon reservoir for a 30 gallon, I was just carting off 4 gallons of runoff per day, with perhaps 6 gallons of input. With my new reservoir, the same watering cycle (30 seconds) put out WAY more water than before, because the reservoir is a little taller, and when the res is full, the water flow coming out of the pump is much higher. So when I got up in the morning and saw that the night's 30 second watering had resulted in about 4 gallons of runoff just from that, something snapped in me and decided this was just too much waste.

So I took that runoff bucket and dumped it back into the reservoir, after seeing that it was only about 200 EC higher than the input. And I dumped in some RO water as well. Overall I'm trying to dilute things down a bit to get input EC under 1000.

It just seemed like if I flushed a bunch of water through that the runoff was probably about like the input enough to reuse some of it.

So I'm wondering if anyone else does a modified DTW where they perhaps recycle a certain percent of it, after measuring the runoff in any way available. I would love to know which nutes are being absorbed and which are building up doing something like this, but I figure that's just what hydro growers deal with.

So - in general, if things are healthy-looking and runoff EC is within 300 points of input, would it be risky or acceptable to routinely take 50% of the runoff, mix it with same amount of RO water and dump it back into the reservoir? I've only got 4-5 weeks left in flower before flushing and harvest, so I don't know I have too long for bad stuff to build up.
 
Z

zebracake

25
3
This article explains it well. For example, phosphorous is consumed at a lower rate than most of the other nutrients so your runoff water will have a higher ratio of phosphorous than your input. So if you're putting that back in then overtime you'll have too much phosphorous, which will lock out micronutrients. The best way to not be wasteful is to dial in your ec with 10% runoff and not letting the medium dry out. I've heard of people doing no runoff but I feel like that would lead to the same problem as recycling.
 
bigbagofbuds

bigbagofbuds

306
93
If you fix the rising EC then you won't have as much runoff to dispose of too. Rising EC means your feeds are too heavy and nutrients are building up, lower the input EC to fix.
 

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