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Why does the ph drop from 6.2 to 4.9 with in a day !?!?

Discussion in 'Hydroponics / Aeroponics' started by JackRush, Jan 31, 2011.


    JackRush Active Member

    My friend has just finished his second week of flowering in a vertical system that looks like this one -> ( http://www.hydroshop.ca/english/ecosystem-vertical-growing-system.html ) . He is using grodan v-slabs made of rockwool. He seems to have a major ph problem now ! Even if he changes his reservoir with fresh new solution, his PH drops by 1.2 points within the first 24 hours !!!!!!!!! He starts if off at 6.2 and everytime the water goes through his slabs it comes back .2- .3 points less !

    Here are some notes that might help u understand his system better

    - He doesn't have a drip system but rather a strong spray at the top of the slabs
    - He sprays 6-8 minutes on and 45 mins off
    - his solution consists of 800 - 900 ppm of A + B from Nutriplus ( http://www.nutri-plus.ca/ ) some PowerPack and some B1 ( he will stop using the last 2 this week )
    - He sets his solution at 6.2 and after just one feed of 8 mins it drops down to 5.9 !! and it keeps doing so until it hits 4.9 within a day or less !

    What should be done ?? I don't think adding ph+ a couple times a day is very good to the plants


    stumps Well-Known Member

    did he set up the the new water and let it sit for a day before going in the rez? could be something in the water going up and down. I hope someone pop's in and explains what I'm trying to say.

    JackRush Active Member

    No he didn't , would that change anything ? I know letting it sit will only get rid of the clorine

    lowerarchy Active Member

    Sounds like pathogens in the rez, possibly growing in the pump/fittings/tubing or something in the reservoir. If he lets it sit in the rez for a day and the pH still starts to go down, that's the issue.

    Otherwise, I'm stumped. No real reason for pH to go down if everything is otherwise healthy and green. I would clean everything thoroughly and blast a new rez with 30%h2o2 at 3ml/l for a while.

    stumps Well-Known Member

    Ph is a strange creature. Have you checked the tds in the water? How do you adjust your Ph? I know if the tds is high it can do strange things when you add utes and such. could even be the nutes doing it. But I'm no expert.

    JackRush Active Member


    stumps Well-Known Member

    I wouldn't drink it. Good is under 200. I can't find my chart but I think 800 is way frigging high. My well runs 195-230. Is that drinking water?

    JackRush Active Member

    My apologies ! The final solution in the reservoir after nutrients have been introduce is 800 ppm. The water itself is around 200 ppm

    supersillybilly Well-Known Member

    If you adjust your ph before adding nutes then thats your problem.

    unity Well-Known Member

    They are taking up more water then nutes, which in turn causes your remaining solution to go 'hot'. It is very normal to get a ph drop the first view days, especially in a new res. if it is a bit 'hot'. What is happening to the ec in that same 24 hour period, that ought to tell you something. If the ec is going up (like I suspect) then just add water back in until you are back at your starting point ec. That should also get your ph back up a bit, the rest you have to adjust with a little bit of ph up, or silica. Next res should be a bit weaker, until you find equilibrium.
    If your ec does not shoot up during the same 24 hours disregard what I told you ;)

    stumps Well-Known Member

    that sounds like a good idea.

    JackRush Active Member

    Ok, the representative from Grodan ( the one who make v-slabs which are especially for vertical growing ) mentioned that since my friend only waters 6 minutes on/ 45 mins off, some roots must be dying since they are not watered enough. He suggested to water 10 on/10 off. He also said that he suspects that the dying roots is the reason why the ph is going down ! !

    What do u guys think ?

    p.s. Unity mention that if the plants are taking up mostly water and leaving the reservoir more concentrated with nutrients that the PH would automatically lowwer. But In that case I guess that the PPM would increase....but that is not the case here. Level of concentration of nutrients remains the same.

    Also keep in mind :
    -this crop is only 3 weeks old
    -the best quality products are use ( a complete nutrient product, Power pack and some B1 ).
    -Reservoir temp is 20-22 celsius ( 68-72 ).
    -Room temp 25 Celsius
    -Co2 is added to the room

    This was not happening in the first 2 weeks !


    The system is not a drip system but rather a " sprinkler " system

    unity Well-Known Member

    Yep, if the ppm doeas not increase my theory is out the window :(

    unity Well-Known Member

    Maybe some rockwool guys can chime in, I have moved on from the stuff years ago due to these kind of problems. Having said that, countless people produce excellent crops with with rockwool. From what I remember rockwool is very finicky with watering intervals, needed runoff etc.

    rosecitypapa Active Member

    Isolate your problem, take your plants out of the equation. Mix up a reservoir of nutes and leave sit for at least 24hrs, adjust ph and keep it sitting until it's stable for 24hrs. If your tds meter is calibrated to potassium your levels are fine but if it's calibrated to sodium, you are running hot.

    jarou Member

    Had similar issue, added the H2O2 @ 3ml per/gal, then 1.5ml per gallon next day and issue resolved... at least with the PH... nothing else noticable!


    GoldPT Member

    Hi guys,

    Im new into the forum! I've started lately into hydroponics with aeroponic system and google directed to this topic since i've exactly the same problem....

    JackRush: I've exactly the same problem... Did you found a solution? I adjust the system to 6.1 and 24h/later it drops to 4.3 :(


    JackRush Active Member

    If I remember correctly, he changed to Canna products which helped a whole lot !!!
    nitro harley

    nitro harley Well-Known Member

    Hey Jack....

    On my last grow I went through this same problem...into my third week of veg my PH started crashing in one day just like you are saying....My plants were green a healthy looking but they weren't growing..the roots were brown and whimpy....They were starting to die....

    I was able to save them with a 29% H202 [email protected] 20ml per gallon for three hours then I pumped the buckets out and did it again for another three hours...then I cleaned everything the best I could with fresh water....Then I added some benny's called actinovate....4 teaspoons in a gallon and a half of water and then I split that up between my six buckets....Then I added fresh nutes and in about three days we had new roots growing the PH leveled out and everything was happy again....hope this helps.......nitro....

    Refusedpanda Active Member

    So the NutriPlus nutes are junk? I have two boxes full of nutes from them I got at a show. I was going to use them next run, but if that shit is causing problems I will just give that stuff away.

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