R/O water What the @#$% is happening with my PH! Help!

Darkset

Darkset

Member
Here's the deal I just decided to try out my General Hydroponics Drip Pods and everything is out of whack! Here's the situation.
  • Plants just moved from nursery into the pods/
  • I'm using pure R/O water starting at PH@absolute 7 and PPM@2
  • Adding in 1/4 recommended General Hydroponics nutrients (and yes it's week enough for my babies I would never try to hurt them :mrgreen: I didn't want the R/O water to leach nutrients from the plant)
  • PH after mix sits right @5.8 with no adjustment needed due to buffers in the nutrients
  • PH holds for a while then begins to climb
  • PPM's are staying constant though out
The PH was climbing up to 7.3 (higher than the water was to start)! I cleaned both pods and clay pebbles as recommended by manufacturer. And have since changed out the water once every two days with fresh solution. The PH is still climbing up to 6.9 after a day or two max in one rez and still to 6.8 in the other. I will readjust only to find it jumps back up again. It is over time peaking out lower and lower but these constant changes aren't going to be good for the girls, and will too much ph down be detrimental even if it is attaining the correct ph? Is this from residual deposits inside the clay pebbles or what? I have no foreign growth in reservoirs and like i said ppm are staying constant whats going on!! Or do I just ride it out and hope it settles over time?
 
Darkset

Darkset

Member
Just for the record, at the moment it doesn't seem to be affecting the plants in a negative way other than a little growth stunt possibly. No signs of distress as of yet but I can't be swinging ph this much so often! Considering going back to old faithful(soil), but really want to get these pods in action......
 
superstoner1

superstoner1

Well-Known Member
Ph swings actually arent bad for the plants, it lets them get the most they can of certain elements at different ph levels. But, that is going too high. What exactly is the ppm? I would guess not enough nutes in the res to buffer the water could be part of it.
 
Darkset

Darkset

Member
The ppm has been stable around 350 +10-. I also made a note to myself that the rez water temp to start is at room temp 68 then after being in action peaks out at 74 max which I assume would raise it a little, but it can't be that much can it?
 
Darkset

Darkset

Member
Nice I see what your saying on the swing, start low 5.5 your getting the Manganese you need then swing up to around 6 when your getting your Potassium and Magnesium while getting everything in between in the process. Now if I can just get it to stay in the range. I did another shot of ph down I only went down to 6.3 from 7 I didn't want to shock anything. It has raised .1 in two hours in both pods. PPM still around 350. Also one pod has no plants in it and is my test pod since water has been an issue so far. So I do changes in this pod first as a safety to gauge reactions to nutes and ph down. At this rate im going to start forming deficiencies up around 7 ph.

 
superstoner1

superstoner1

Well-Known Member
Actually at early veg you can have defs over 5.9 because of what they need. Dont worry about shocking them, set the ph. On your test pod try raising the ppm to 550-600 and see how the ph does.
 
Darkset

Darkset

Member
Here's the numbers to start this morning. Both pods down 3quarts

Left pod (control)
  • pH @ 6.8
  • PPM @400 (assuming from water evap)
Added water, Upped the nute concentration to 665
  • buffers in nute only brought pH down to 6.4
  • 2ml of pH down to stabilize at 5.4
  • PPM @670

Right pod (active)
  • pH @6.6
  • PPM @390
Added water NO additional nutes
  • 3/4ml pH down to stabilize at 5.5
  • PPM 410
Going to check numbers ever hour on the hour to monitor. Did notice higher nute concentration pod took substantially more pH down to knock it down about the same amount as the regular pod. Is it going to be harder for the pH down to do its thing the higher the ppm even with the nute buffers? Couple of pics to keep this from being too boring ;)
 
Darkset

Darkset

Member
Left pod (control)

  • pH @5.6
  • PPM @689

Right pod (active)

  • pH @5.7
  • PPM @425
That's a good rule of thumb to remember on the double per ph!

 
Darkset

Darkset

Member
Left pod (control)

  • pH @5.8
  • PPM @675

Right pod (active)

  • pH @5.8
  • PPM @455

Things seem to be finally settling out, but it has held for a few then jumped again before so we'll see......
 
cannabineer

cannabineer

Ursus marijanus
When I ran a hydroponic grow (NFT technique, common reservoir) using salt nutes of my own device, I added a non-nutrient buffer salt. Even so, my pH rose fast enough that I needed to bring it down daily by 1/2 to 1 pH point. (I used nitric acid.) I have since learned that it had to do with ion balance. When the plant takes up more anions than cations (which was my case because I used only nitrate as the N source) the res pH will go up. GH Grow has 7:1 nitrate to ammoniac nitrogen; the Micro has 15:1. With those ratios I would expect a pH rise, especially with actively growing plants in veg. My 2¢ ... cn
 
Darkset

Darkset

Member
So in theory with the control pod (no active growth just evaporation), shouldn't it at one point reach a threshold and finally maintain the pH I want it at?
 
superstoner1

superstoner1

Well-Known Member
There really can't be enough evaporation to be a noticeable difference in levels. If so then u have other issues.
 
Darkset

Darkset

Member
I currently have pumps for drip running 24/7 should I put it on a half hour every hour schedule? In 24hr just under a quart has evaporated from both and levels are at.
Big change over night this might be the info we're looking for.

Left pod (control)

  • pH @6.5
  • PPM @680

Right pod (active)

  • pH @6.0
  • PPM @455


The pod with the stronger nutrient solution made a huge jump overnight. PPM hasn't changed much, and water temp at 75 degrees.

Note:When water was added yesterday water temp dropped to 72 then rose back to 75 as expected. Level change from temp would be depicted at the 4 hour mark results (when temp reached 75).
 
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