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HELP! DWC Hydroponics water PH drops over time

Yeah, he isn't totally wrong, but he seems to think that the buffer is less stable than most other sources. I link to him especially because he grows in particularly small containers and really demonstrates that container size is irrelevant to the size of the plant in Coco.

And I agree that pH is altered by certain exchanges in the media. But I believe that pH can be buffered as well. I believe that the difference in the water that you described is a result of the different capacities of the starting waters to buffer pH. For example, it takes a lot less pH down to adjust a gallon of RO water from 7.0 to 6.0 then it would to lower well water the same amount. The RO water would be stable at the new pH quickly and the Well water would take a while to stabilize. This is a result of the water's capacity to buffer the pH.

EC rises in the media because of the removal of water through evaporation and transpiration. The nutrient exchanges with the plant have minimal impact on the EC of the solution.
 
Thank you Campesino, so nice that you are able to translate info to layman terms..:)

I was thinking exactly this as you stated in your coco grow:
"EC rises in the media because of the removal of water through evaporation and transpiration. The nutrient exchanges with the plant have minimal impact on the EC of the solution."

Agreed on the buffer of both the Well and RO. One of my theories is that yes that roots do an ion exchange that can offset it's stable state, however the nutrient solution is also exposed to the air which does a little exchanging CO2. So the nute solution is always trying to reach pH of 7.0 unless super buffered. So in theory the nute solution should remain stable if properly buffered, yet the actual EC raising is NOT due to the addition of more salts (unless no proper runoff), but due to the evaporation of water which makes it appear that there is more salts.. Like a traffic jam, all the autos are the salts and not enough road is the H2O of sorts..haha

Apologies FlyingDutchPaddy for sub-thread highjack, just helps me to write this mess out..
 
Sockfilter Yes, that all sounds pretty good.
pH certainly changes as a result of interactions between the nutrient solution and the plant and media. In general these changes are not problematic and can be ignored. pH of inflow should be adjusted - pH of run-off should be ignored
EC doesn't change because of interactions with the plant. EC can change due to interactions with the CEC of the media - but shouldn't in properly buffered Coco. Therefore, Evaporation is responsible for the changes to EC - and EC should always be higher in Run-off than Inflow. Run-off prevents it from becoming too much higher.
Finally, if the EC of run-off is lower than inflow in Coco - this indicates that the CEC is not buffered and the Coco is still stripping Ca and Mg from the nutrient solution.

Apologies for continuing the hijack - and Cheers to all
 
Friday afternoon update, 20180615 at 17:20 - pH = 5.7
topped up with 1.5l of nuted water that measured 6.9.

will let that circulate through the system so it settles...
comment later on what it stabilises to...
 
I think you'll be happy that you made the investment. It will really help you to know what is going on and allow you to fine tune your grow!

I'll be happy to help if you have any questions :)
 
New week, new monday... new measurment... :)

20180618 at 19:00 - pH = 6.0

0.2 drop over about 25 hrs...
2 of 3 plants starting to look ready... :)
3rd 'mystery' plant is growing big.... lots of budsites...

spots on leaves seem to have stopped spreading...

will need to change water tomorrow, been 10 days now since last complete change.
 
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Tuesday 20180618, change all the water day... receive TDS meter day :)

TDS meter is NaCl (salt water) factory calibrated to 342 ppm

2 measurements before the water change: pH & ppm.
Before changing water pH measured at 5.7
Standard tap water ppm = 244

So, change of water details:
Quantity = 45 L
3x 15L , per 15 L measurements were:
micro - 30 ml - ppm 596 - pH 7.3
Bloom - 60 ml - ppm 737 - pH 6.3
CalMag - 30 ml - ppm 669 - pH 7.4

After adding all 45 L to res & buckets,
average ppm = 645
average pH = 7.5

waterpump & air stones on for 10 mins;
ppm = 653
pH = 7.5

Added 8.5 ml pH down, let it circulate for 30 mins.
ppm = 650
pH = 6.5

Resting pH after plants were put back in at 20:45 - 6.7

Will see what happens overnight...
 
FlyingDutchPaddy said:
Tuesday 20180618, change all the water day... receive TDS meter day :)

TDS meter is NaCl (salt water) factory calibrated to 342 ppm

2 measurements before the water change: pH & ppm.
Before changing water pH measured at 5.7
Standard tap water ppm = 244

So, change of water details:
Quantity = 45 L
3x 15L , per 15 L measurements were:
micro - 30 ml - ppm 596 - pH 7.3
Bloom - 60 ml - ppm 737 - pH 6.3
CalMag - 30 ml - ppm 669 - pH 7.4

After adding all 45 L to res & buckets,
average ppm = 645
average pH = 7.5

waterpump & air stones on for 10 mins;
ppm = 653
pH = 7.5

Added 8.5 ml pH down, let it circulate for 30 mins.
ppm = 650
pH = 6.5

Resting pH after plants were put back in at 20:45 - 6.7

Will see what happens overnight...
Click to expand...

You shouldn’t be putting those plants back in the system until you’ve stabilized that PH at 5.8-6.0....

to be clear once more, in Hydro, never let your PH stray outside of 5.5-6.5. It’s a shock to your root PH to take them out of 5.7 water and throw them into 6.7 water IMO
 
Saturday early update 20180623 at 11:15.
pH = 5.9
ppm in bucket 1 - 687 (no plant)
ppm in bucket 2 - 686 (small size indica strain)
ppm in bucket 3 - 685 (larger size indica strain)
ppm in bucket 4 - 692 (big bushy girl, i think sativa strain as general color is a bit lighter than the other 2)
ppm in main res - 685
 
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