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HELP! DWC Hydroponics water PH drops over time

Update for this evening, @ 20180610 19:00 - pH = 5.8

earlier this afternoon around 16:00 i measured 5.7 so I filled up with 1 L of nute water (1ml micro / 0.3 ml gro / 1.7ml bloom) at pH 7.0
just topped up by another 1 L of plain water @ pH 7.3.

will check again in 2 hrs just before lights out.
 
You’re on it brotha! Keep it rocking and you’ll be pleased at harvest! Is it just me or does the res seem to be stabilizing a bit?
 
Hi IslandColas ,
I’m keeping a close eye on it during the weekend...
Now that Monday is approaching, can only measure & take corrective action in the evening...

But it seems to be on target now after adding a L plain water & 1 L nuted...

Thanks for the comments :)
 
Please keep me posted as much as you can. I only check my reservoirs once daily during the week as well. I’m near positive it will stabilize if you just continue your small adjustments and continue to change your reservoir every 7-10 days
 
Monday evening update. 20180611 @ 18:35 - pH = 5.3

Added 1L of water containing:
20ml CalMag
20ml pH up
20ml H202 (12%)

pH of that L was 11.1

will measure pH again before lights out to see what it stabilises on.
 
current reading @ 20:45 - pH = 6.1

IslandColas, @Campesino,
I have an idea about what may have been happening.

the pump that is recirculating the water from the main res was sitting on the bottom, exact same level as where the drain hoses from the buckets were coming back to the res.

i have a feeling that the water being recirculated was not properly remixing with the water already in the main res, causing this rapid drop in pH over a few days.

what i've done is raise the pump to just under water level in main res leaving enough for consumption of the plants/evaporation so its doesnt go dry.

would you have other idea's about this?

thanks :)
 
FlyingDutchPaddy said:
current reading @ 20:45 - pH = 6.1

IslandColas, @Campesino,
I have an idea about what may have been happening.

the pump that is recirculating the water from the main res was sitting on the bottom, exact same level as where the drain hoses from the buckets were coming back to the res.

i have a feeling that the water being recirculated was not properly remixing with the water already in the main res, causing this rapid drop in pH over a few days.

what i've done is raise the pump to just under water level in main res leaving enough for consumption of the plants/evaporation so its doesnt go dry.

would you have other idea's about this?

thanks :)
Click to expand...

If can, I would make the drain hoses introduce the water from the top of the reservoir and keep the pump at the bottom. This ensures you have a full mix of your nutrient solution before it gets sucked back into your buckets. You could also use waterfall effects to achieve extra aeration/agitation.
 
I just did a quick search on your particular rdwc system. The diagram that the company provides shows air stones in the individual grow buckets but I don’t see one shown for the reservoir, does it have an air stone that I don’t see in the diagram? I setup my own system with a similar design but I use an air stone in the reservoir to churn the nutrient solution as it drains back into the reservoir.
 
I have used GH Flora trio for 3 years in my RDWC system. Total capacity is 25gal. My well water is 6.9@ 45ppmTDS I think that GH uses pH buffers to target pH around 5.5 when mixed with RO water. I tend to start at 5.5 and then use pH up to drift towards 6.5 over the 10 days between fluid change.
 
From what I have read and have experienced first hand in a true Hydro setup, although not technically CEC, it does show that pH can be affected simply by the plants doing what they do. Now a fast shift in pH is a different issues and I think that is what is happening here with FDP.

"So, while water is somehow "pushed" inside plants, ions are litterallh captured by them.
We just said that water inside roots is quite rich in ions, and this is a key point. Some of those Ions are micro and macro elements that were already adsorbed, while others are simply H+ and OH- resulting from water dissociation.
Since like every Ion, micro and macro element ions in solution have their own electrical charge (K+ for example) plants can't just "take" them, otherwise equilibrium would be broken. What they actually do is swap them with equivalent amount of H+ and OH-

For exemple

potassium (K+) swapped with 1xH+
calcium (Ca++) swapped with 2xH+
magnesium (Mg++) swapped with 2xH+
ammonium (NH4+) swapped with 1xH+
iron (Fe++) swapped with 2xH+
manganese (Mn++) swapped with 2xH+
zinc (Zn++) swapped with 2xH+
nitrates (NO3-) swapped with 1xOH-
phosphates (HPO4--) swapped with 2xOH-

In this way electrical charge equilibrium remains the sama and at the same time, roots releasing H+ or OH- make pH fluctuate.
This is a well known behavior for hydroponic growers, where there is quite no buffering power in the media to oppose to this."
(https://www.icmag.com/ic/showthread.php?t=307683)

So as I wrap my head around the science of this process, thought I would post this for those who are looking for answers as to why..:)
 
Agreed on the return nutes.

I had a 4'x4' flood and drain table with 40gal rez feeding the table. The return just drained back into the rez by free falling and splashing into the rez (yes lid on it). That creates more O2 in the rez.

Also on the pump within the rez, I added another small pump just to keep the rez constantly mixed up, combined with the vast surface area of the res, O2 was naturally absorbed and I never had to run an air stone and pump.

However keep in mind that this was a big rez that could handle and dissipate the additional heat the extra pump introduced into the rez..

More than 1 way to skin a cat and just throwing out other ideas that may or may not be useful in your endeavor

Sounds like you are dialing it in FDP..:)
 
Hey Sockfilter
Yes, DANGERDAN and I discussed "The Cook" and his science. There are problems with it. As DANGERDAN pointed out, literally nobody else makes the arguments that he does! He knows some chemistry, but a lot of what he says disagrees with plant science - especially regarding buffering.
I would have to look deeper at this again, but I no longer trust The Cook as a reliable source.
 
Obi-Wan , from the manufacturer it comes standard with 4 air stones for the buckets, indeed. There is no 5th airstone for the main res.
i suppose i could get another air pump and put the spare airstone in the res...

thanks for the idea
 
pH for this evening ; 20180613 at 18:30 - pH = 6.0 in main res & one bucket.

only 0.1 drop in pH... seems to be stabilising... but needs a watchful eye.

will comment with again just before lights out.
 
Understood Campesino, Yes the Cook's info is several years old and the times do change as well as the understanding to what makes all this stuff work, I see you sourced some of his info as well in your guide to growing in coco, so some of Cooks may be legit or you dont trust period. Again I am no scientist, just trying to figure out what makes it all tick.

Buffering of growing medium aside since this thread is based on DWC, are you saying that in a properly setup hydroponic system with spot on environment, that the pH of a rez should not drift over a few days, even with the plants roots exchanging ions within the solution for nutrient uptake while leaving the salts to build up creating a higher CE?

I do see how our solution can change over time, heck even minutes in some solution makeups.

Example I have run 2 side by side test in my search for the the perfect nute solution makeup for minimal pH adjustments, if any.

(2) 1 gallon jugs
The difference is the source H2O:
1 gallon has 99% RO with a splash of well to reach a starting PPM of 25. Added 3ml calmag (PPM now at 270), 1ml micro, 3ml bloom and 1ml koolbloom.
1 gallon has 100% well H2O with heaps of Ca/Mg starting out at 235 PPM. Added 1ml calmag (PPM now at 305) 1ml micro, 3ml bloom and 1ml koolbloom.
*(the difference in calmag dosage is my trying to replicate as close to equal cal-mag starting PPM between the RO and Well)
After letting them rest, I test each one for pH.

The RO comes out right around 6 pH and stable.

The Well comes out a tad lower than 6 (5.5-6.0). using old school Ph indicator solution (yellow, with a hint or orange) yet within 5 mins the color shifts to a heavy green indicating a pH in the realm of 7.0ish. SO just trying to make sense out of this and my limited knowledge would suggest that the Well nute solution while sitting in the open air is sucking up O2 from the air as it ties to establish equilibrium in the exchange of ions, thus the change in color?

Thanks for entertaining my limited scope in my quest for knowledge..:)
 
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