PH confusion???

[waterdawg]

I have 2 trays (flood and drain) going, one is 12/12 for 25 days and the other is 12/12 for 10. the issue I am having is in the 10 day tray. I fill the res using tap (well) water that is around 7.4 and have always added 75 mils of PH down which brought it down to 6.5ish then I would add a capful at a time, usaully 3 to bring it just under 6. I ran out of the stuff I used (no labels, or strength, or even what it was) and bought some new 17% phosphoric acid. Now Ill add like 100 mils and it doesnt move so Ill add another 50 mils and it will drop .5, Ill add another 50 and again it will drop .5, Then Ill add another 50 and it plummets to like 4.5 and I have to drain the res. Does anyone know why this is happening. I have had to drain res twice now but oddly enough I added 75 mils to the 25 day res and its ok, running around 6-6.2.

 

[racerboy71]

why not just get some ph up as well, that way if you dip under what you're shooting for you won't have to drain the entire system, but rather you can simply add some up until you get to your goal..

how long are you waiting in between measuring the ph each time after making an adjustment?? i'd try and give it a good half an hour or so after you add any ph solution before measuring it to allow it to balance out nice and even, this way you're not chasing your tail as much..

 

[RetiredMatthebrute]

yeah my guess is about the same, your measuring too quickly

 

[nick88]

different brands are diff percentage... also noticed stuff like potash or phos additives cause ph 2 harder to bring down

 

[THunderC]

My first recommendation would be to stop using well water for hydroponics. Correct me if I'm wrong but I believe this is usually advised against. For my organic fert teas and my DIY bubble cloner I simply go to my grocery store and utilize the "culligan" station and purchase some nice R/O water for about $0.29 a gallon. If you can't acquire R/O water distilled is an safe alternative.

I'm not certain but I have to assume it would be easier to monitor PH in water that doesn't have an unknown amount of many different minerals. I also keep PH up and down stocked in case I find myself chasing that perfect number.

Best of luck,

THunderC

 

[waterdawg]

My first recommendation would be to stop using well water for hydroponics. Correct me if I'm wrong but I believe this is usually advised against. For my organic fert teas and my DIY bubble cloner I simply go to my grocery store and utilize the "culligan" station and purchase some nice R/O water for about $0.29 a gallon. If you can't acquire R/O water distilled is an safe alternative.

I'm not certain but I have to assume it would be easier to monitor PH in water that doesn't have an unknown amount of many different minerals. I also keep PH up and down stocked in case I find myself chasing that perfect number.

Best of luck,

THunderC

Yes your right RO is the way to go but in my situation it would not be possible as my grow is remote from house with no pressurized water and buying it is out of question as I have now 3 res's at 45 gallons and soon will have one more. I perhaps have not been waiting long enough but the strange thing is the other res is doing ok the only difference is strain and the massive roots. The tray I'm having issues with has suffered due to inability to stabalize the PH. I did try using PH up at one point to raise it but 4 hours later the girls started to curl up real bad and again I drained the res!! I think I will have to just monitor it more closely. Is it possible to get 100% phosphoric acid or would that put me on the terror list??? . Also I called the guy at shop and he is trying to get original stuff. Its just real strange that new tray causing all these problems but yes again well water is a bitch with a hydro setup. Thanks for suggestions.​

 

[cannabineer]

I have 2 trays (flood and drain) going, one is 12/12 for 25 days and the other is 12/12 for 10. the issue I am having is in the 10 day tray. I fill the res using tap (well) water that is around 7.4 and have always added 75 mils of PH down which brought it down to 6.5ish then I would add a capful at a time, usaully 3 to bring it just under 6. I ran out of the stuff I used (no labels, or strength, or even what it was) and bought some new 17% phosphoric acid. Now Ill add like 100 mils and it doesnt move so Ill add another 50 mils and it will drop .5, Ill add another 50 and again it will drop .5, Then Ill add another 50 and it plummets to like 4.5 and I have to drain the res. Does anyone know why this is happening. I have had to drain res twice now but oddly enough I added 75 mils to the 25 day res and its ok, running around 6-6.2.

It sounds to me like you are fighting the buffer point (pKa) of both phosphoric and carbonic acids. The carbonic/bicarbonate pKa is 6.35. The monophosphate/diphosphate pKa is 7.20. Once you pass a pH of 6 on the way down, you're in the slide area. cn