PH rising in handwater solution

[greentrich]

Hello all.

Quick question here.

My method is hand watering to waste. I mix up about 3 gallons of solution with nutes and balance to about 5.9-6.0 (in coco). Have to use PH Up to bring it up there after the nutes are added. Last night, after using about 1 gallon I re-checked the PH of my solution just out of curiosity. After about 20 min it had risen up to about 6.2. So I added some Down to take it back down to 6.0. 1 gallon and about another 20 min, it's back up to 6.3. This is all in the bucket of solution, not the runoff.

So, after using the entire solution up I mixed another 3 gallons. Did not use any of it as an experiment and just let it sit there. 20 min later...it's up to 6.2 again.

Why does this happen to solution just sitting in a bucket??? Anyone else have this happen? I backed up the results with test strips and re-calibrated my meter with the same results. I even replaced the probe on my meter just to make sure. I use Botanicare nutes and honestly don't know if this has ever happened on the previous projects. Does PH UP take time to dissolve or take full effect?? The only difference from this and previous projects is that I am using a lot more water than before...does that have an effect??

I'm very confused and am wondering if this is causing some minor issues I am having. I can't understand how I can balance a nute solution to a particular point, and 20 minutes later...without using any of it...it jumps up at least .2 points. To top that off, I let the new batch sit longer, and the PH just kept rising.

What the hell is happening??? Will it ever stop rising? I decided to let the new solution sit overnight just to see how high it rises in 24 hrs.

Also, this is with RO water starting at 7.25 if that helps.

Thanx for any insight.

 

[Grigori]

Also, this is with RO water starting at 7.25 if that helps.

If the ph of your ro water is that high sounds like you have some very alkaline water. Usually after source water runs through a ro unit it comes out with a lower ph, like 5.8-6.2. My tap water's ph is 7.4-8.2 but comes out of the ro at around 6.0, give or take.

Have you ever just tried to add the nutes to the water, no ph-up and let it sit? Try that and see how high it rises, and adjust from there.

 

[greentrich]

If the ph of your ro water is that high sounds like you have some very alkaline water. Usually after source water runs through a ro unit it comes out with a lower ph, like 5.8-6.2. My tap water's ph is 7.4-8.2 but comes out of the ro at around 6.0, give or take.

Have you ever just tried to add the nutes to the water, no ph-up and let it sit? Try that and see how high it rises, and adjust from there.

It's a brand new RO unit. In the spec it says supposed to come out at 7.5, and it does. I am used to what you mentioned...RO being in the high 5's to low 6's. Maybe there's something with new RO units they are doing to make it neutral for consumption??? I don't know.

I have let the solution just sit without balancing. That was one of my methods with the last experimentation batch. It didn't move over the course of 45 min. Then I added the UP...20 min later up it kept going.

Thanks for the thoughts!

anyone else??

 

[redheadfreakin]

Most nutrients are ph buffered.
You should rarely have to add any ph up/down unless you are under 5 or over 7.
Let it be...

 

[greentrich]

Most nutrients are ph buffered.
You should rarely have to add any ph up/down unless you are under 5 or over 7.
Let it be...

OK...well check this out. My initial water is around 7.2 to 7.5. When I add nutes to add up my desired level which at this stage is around 1100 to 1200 (5th week of flower), the PH drops to around 3.0. Hence needing to add PH UP. Now does THAT make any sense either?? This is my normal feeding and never checked the PH after the initial balancing.

Last night is when I noticed this because I wanted to flush due to some minor issues. So I mixed a very low solution of 200 PPM...cal/mag and pro bloom. This dropped the PH to about 5.0. Added a bit of PH UP to bring it to 6, this is when I noticed all this stupid stuff.

 

[redheadfreakin]

What nutes are you using and what conversion factor are you using for ppm?
EC is universal if you can relay that...

 

[greentrich]

my nutes are all Botanicare PBP line....cal/mag+, bloom, and hydroplex. Last night when I noticed this I was only using calmag and pbp bloom.

Don't know the conversion factor...not that schooled in it yet. I know its a Hanna combo meter if that helps. Thanks redhead.

 

[redheadfreakin]

I have never seen PBP drop ph THAT much.
You said you calibrated and checked ph with strips.
What about ppm?
I'm wondering if your ppm is way higher than what is reading.
Any backup way to check that?
Something isn't right...

 

[greentrich]

I totally agree redhead. Something is weird. This is my third time around the block and have never seen the ph drop that much...with ALL the same methods used in the first two. Granted...I am mixing more nute solution, 3 gallons on this one compared to 2 on the previous ones, but that shouldn't matter should it?? I mean PPM is PPM, regardless of the amount of water.

I don't know of any other way to back up the PPM readings. Tonight I planned on recalibrating the PPM reader just to double check, but I usually only have to do that when I start again. Then through the grow it's been fine.

 

[redheadfreakin]

Ya, recalibrate, make sure your RO is reading 0 or close to, check again...
Other than that, I am stumped for a reading that low on unused solution.

 

[greentrich]

will do redhead. RO actually comes out at 30 PPM to start with. Which is better than RO water bought from the water store down the street. I'll be back tomorrow with results.

Thanks for your time.

 

[generalgrievous]

how long do your nutes sit around after mixing before they get used up...?

a ph dive like that after everything was mixed and stable has me thinking your nute solution is possibly going anaerobic... i would stick in a small airstone with an aquarium pump, aerate your 3 gl. of solution while you work with it and see where your ph levels off with oxygen in your nutes...

 

[greentrich]

how long do your nutes sit around after mixing before they get used up...?

About 30 sec. Enough time for me to fill my watering can. Whatever doesn't get used, which usually isn't too much, gets dumped. I don't like letting solutions sit overnight unless it's for some particular reason i.e. short on nutes, water, or patience.

Something is outta wack though. A PPM solution of ~1100 shouldn't bring the PH down a full three points or more should it? On top of that, it seems I need to use an absurd amount of PH up to bring it up. Then I noticed it rising all by it's lonesome. Does PH Up take time to dissolve in larger quantities of water?

I might try a different source of water tonight.

Thanks General

 

[greentrich]

OK...well the consensus is:

I'M AND IDIOT.

Turns out if you just chill the fuck out, and let the PH up do it's job, in less than 5 min it stabilizes.

Here's what I did last night. Mixed a new batch of around 600 PPM which put my PH at about 3.9 (started at 6.8), added about a tsp (5ml) of Up. Brought it up to about 4.8. THEN I let it sit for about 3 min went and did a couple things, came back and it was up to 5.5. Whoa. Ok, so I added a touch more, went up to 5.8, waited another few min...6.0 on the nose. This measurement did not change over the course of fertigation....thank Horace.

Apparently I wasn't letting the PH do it's job and bring the water up all the way. So while it was still adjusting the alkalinity of my water, I would add more and more. Well needless to say by the time it all caught up with itself I ended up at around 6.5. Good job asspony.

I've read it a million times and this proves it: patience. In this hobby you need patience...especially while you are balancing water.

I do have one other issue that has already been pointed out. That is the nose dive my PH takes from "empty" water to a nute solution. The PH out of my RO has dropped a bit to about 6.8. But like I said above, mixing a solution of ~600 PPM, drops the PH to the high 3's. If I try to double that to ~1100...high 2's, which in turn need an assload of UP to balance it out.
Anyone have an idea on this one?? And should I be starting another thread somewhere for this issue? I don't remember this being that severe the past couple grows. But I can say that the outcome is the same whether it's water out of my RO unit or water bought from the H2O store. Fact of the matter is the PH drastically drops when a full solution is applied. And I don't think it's normal.

If need be I will start a new thread for this, possibly in the handwatering coco section.

Redhead,
You had mentioned earlier that most nutes are buffered and to "let it be". Does this mean to let the solution be until it rises naturally or does that mean not to balance the solution and just continue to water?

Thanks to everyone, for your time, attention, and input.

 

[redheadfreakin]

Redhead,
You had mentioned earlier that most nutes are buffered and to "let it be". Does this mean to let the solution be until it rises naturally or does that mean not to balance the solution and just continue to water?

Ya, wait a while before adding any ph up/down and let the nutrients stabilize.
Most often you won't have to add any ph up/down.

 

[greentrich]

K redhead...I tried that. Mixed a batch and let it sit 24 hrs. Ph and PPM were still the same as when originally mixed.

Last night I mixed AND balance a batch to let it sit 24 hrs. I expect the PH to rise maybe a couple hundredths or maybe a full tenth of a point but nothing major. I'll find out here in a couple of hours when the garden comes on.

Thanks for the time everyone. Water chemistry is FUN!!

 

[greentrich]

Yet another update: OK, so Sunday night I mixed a solution at 900 PPM and balanced it at 5.6 (accounting for the rise. My target is 5.9-ish). Walked away for 24 hrs, walked in last night, took a reading and it was up to 5.98. Wow...a full 3 tenths of a point!!! PPM had dropped just a touch as well.

Now this is strange to me. Letting the solution sit overnight if anything should have brought the PH down and the PPM up shouldn't it have??? My logic here is water is sitting out in the open and, especially with a dehumidifier in the room, the evaporation of the water only should have left a more concentrated solution with a lower PH...even if it was a little bit. I never expected it to rise, especially that much.

This is strange.
Anyone have any thoughts on this????

 

[KlagDragon]

What are you using for pH up/down? The powder, or liquid?

 

[greentrich]

GH PH Up liquid. Never noticed this issue before, then again...wasn't looking for it.