pH keeps climbing WTF?

CatManDoo · Nov 14, 2010

I know there's all kinds of posts like this but I just thought I'd vent here.

And I know everyone will say, "go out and get a RO filter" or "just go to the store and buy it for .35/gallon. But with hydro that gets hella expensive.
I did do that last change and the pH was steady and I never even had to adjust it all week. But damn! There's got to be a way with tap water. What kind of magic spells do they do on this stuff to make it keep going up every 12 hours!? This time I even took it way down to like 4.5-5 then brought it back up to 6 hoping to kill the buffer or something.
I'm reconsidering soil.

ibjamming · Nov 14, 2010

Did you try feeding more? What's the EC?

highonmt · Nov 14, 2010

It sounds like you might have hard water that is buffering to a high pH. Mine does the same thing so I bought an ro flter...but you could also try one of the hard water specific nutrients.

Or you're running the EC too low and your plants are eating enough of your nutrients to drop the PH. You should be at 1.2 EC to 2.0 ec. More details like system, type of nutrients etc. will bring more help.
HM

CatManDoo · Nov 14, 2010

EC

EC

This is my first hydroponics attempt so I havent been able to invest in every do-dad like the EC yet. The thing is, the pH will change as quickly as 12 hours after it is a brand new round of water and nutes and the reservoir level hasn't noticeably changed nor water temperature. Doesn't hard water stain your sinks and toilets? I don't have that problem here. It does taste sort of sweet though. Out of the sink of course. I haven't tried the toilet water but I'm sure it's the same

CatManDoo · Nov 14, 2010

highonmt said:
More details like system, type of nutrients etc. will bring more help.
HM

OK, I'm using the General Hydroponics nutes Grow,Micro,Bloom. DWC Bubble buckets not connected. Keeping temps manually with frozen waterbottles daily at 68-70(2).
Oh and I have also tried letting the water sit for 2 to 3 days before I use it too.

scurred · Nov 14, 2010

You're doing hydro without a TDS or EC meter? Go buy one for $30, do yourself a favor. That's really a necessity to a successful hydro grow.

And just so you know, I use RO and have the same issue. pH will rise from 5.5-5.8 to 6.0-6.3 every day, it's as simple as checking it once a day and adjusting with 1-2 drops of pH down. Not the end of the world.

You should be noticing growth at twice the speed of your soil grows, which makes the 5 minutes a day you spend checking/adjusting pH worth it.

Letting the water sit out just lets the chlorine evaporate. It won't fix the pH, the unstable pH is probably caused by 1 of the other *who knows how many* chemicals/things they add to our tap water.

buddin_904 · Nov 14, 2010

pH keeps climbing....because of your "bubble buckets" the airstone is whats causing this

i am unsure of this myself....if you pH your nutes to like 6 lets say....then dump them in a bucket or rez with an airstone...the pH will rise due to the introduction of dissolved O2....

what is the real answer to this problem....do people run pHs of like 8-9 even though they know the un-airstoned solutions true pH is correct???

my experience is using a airstone for liek a couple days and it blew my pH through the roof...did away with it and never knew the answer to my question....

if anyone that knows what im talking about could respond with experienced advice I would appreciate it...thanks!

highonmt · Nov 14, 2010

buddin_904 said:
pH keeps climbing....because of your "bubble buckets" the airstone is whats causing this

i am unsure of this myself....if you pH your nutes to like 6 lets say....then dump them in a bucket or rez with an airstone...the pH will rise due to the introduction of dissolved O2....

what is the real answer to this problem....do people run pHs of like 8-9 even though they know the un-airstoned solutions true pH is correct???

my experience is using a airstone for liek a couple days and it blew my pH through the roof...did away with it and never knew the answer to my question....

if anyone that knows what im talking about could respond with experienced advice I would appreciate it...thanks!

Whoa cowboy it aint the O2 that is affecting the ph I won't bore you with a freshman chem lecture... but the airstones got me thinking back to the wally world "stones" (actually sand?? and epoxy) that I used in my first dwc. They did cause weird ph issues like this as they softened and fell apart. Do you have blue airstones. If you do you might also want to try diffusers instead, they look like fat spongy dripline.
HM

buddin_904 · Nov 14, 2010

i had the blue one.....eh??? oh and please do bore me with your chemistry knowledge...considering it wont bore me a bit......

how can you say it aint the O2 that is effecting the pH....adding more O2 to a water solution will raise the pH......

scurred · Nov 14, 2010

highonmt said:
Whoa cowboy it aint the O2 that is affecting the ph I won't bore you with a freshman chem lecture... but the airstones got me thinking back to the wally world "stones" (actually sand?? and epoxy) that I used in my first dwc. They did cause weird ph issues like this as they softened and fell apart. Do you have blue airstones. If you do you might also want to try diffusers instead, they look like fat spongy dripline.
HM

Talking about alternatives to the standard blue airstones, such as these?

http://www.htgsupply.com/viewproduct.asp?productID=55703
http://www.htgsupply.com/viewproduct.asp?productID=55690
http://www.htgsupply.com/viewproduct.asp?productID=56106

Much more expensive. Could this be the cause of my DWC's pH rising as well?

ambertrich · Nov 14, 2010

No, it is not the materials used to make the airstone breaking down and causing the ph to rise. These things should be chemically inert.

What may be happeing is that over time the level of dissolved CO2 in solution will cause the solution to become more basic-i.e. the ph rises.

You should use a ph down that has good buffering capacity to slow the rate of ph rise. I like GH ph down - buffers well and is a phosphoric acid based product. Some ph down solutions are a nitric acid based product which is fine in veg, but I don't like to use those is flower (esp late in flower) as these can add a small amount of N to the nute soln when I am trying to starve the ladies of N.

Hope this was of some help.

Good luck with your grow.

Daffy · Nov 14, 2010

The plant and microbes releasing enzymes that increase the pH thus making nutrients available. Add pH down.

spurr · Nov 14, 2010

CatManDoo said:
I know there's all kinds of posts like this but I just thought I'd vent here.

And I know everyone will say, "go out and get a RO filter" or "just go to the store and buy it for .35/gallon. But with hydro that gets hella expensive.
I did do that last change and the pH was steady and I never even had to adjust it all week. But damn! There's got to be a way with tap water. What kind of magic spells do they do on this stuff to make it keep going up every 12 hours!? This time I even took it way down to like 4.5-5 then brought it back up to 6 hoping to kill the buffer or something.
I'm reconsidering soil.

The problem sounds like your water alkalinity (e.g. amount of Ca and Mg ions as bicarbonates and carbonates) is too high, ex. > 100 ppm. Over 80 ppm is about as high as you want to go. Using RO water is a poor idea due to it's low pH buffering ability due to lack of water alkalinity.

Call you local water authority and ask them what the water alkalinity is. If it's > 80 ppm then filter your tap water though a fairly dense bit of plain sphagnum peat moss to reduce alkalinity. Ideally your water should have alkalinity of 40-60 ppm to prevent pH swings up or down.

spurr · Nov 14, 2010

ambertrich said:
What may be happeing is that over time the level of dissolved CO2 in solution will cause the solution to become more basic-i.e. the ph rises.

You have that backwards, Co2 + water = "carbonic acid". And carbonic acid reduces pH because it's a weak acid (this is a source of acid rain). This is why pH of distilled water is not 7, it's from ~5.8-7 depending on the amount of Co2 in water, i.e. amount of carbonic acid.

spurr · Nov 14, 2010

Daffy said:
The plant and microbes releasing enzymes that increase the pH thus making nutrients available. Add pH down.

Roots exude both acidic and basic substances, as do microbes. When roots take in ammoniacal nitrogen (ex. ammonium) they exude H+ protons (acidic) and when roots take in nitrates they exude bicarbonates (basic). And cannabis ferts have much more nitrates than ammoniacal N (i.e. ammonium), thus over time cannabis fets will make plants increase pH in water due to exudation of bicarbonates more than exudation of H+ protons.

Roots also exude other weakly acidic substances (such citric acid) that reduce pH. Not only that, but when roots (and microbes) release Co2 they create carbonic acid (Co2 + water) and that lowers pH too. But then some bacteria exude "carbonic anhydrase" to dissociates carbonic acid back into Co2 and water because they prefer a more neural to basic pH...a big game of tug-of-war! Neat stuff, huh?

ambertrich · Nov 14, 2010

spurr, you are absolutely correct, I have it backwards. Thanks for the heads up.

spurr · Nov 14, 2010

NP

Glad to help

buddin_904 · Nov 15, 2010

SPURR you seem to know some chemistry.....when you bubble a solution with an airstone wont the pH rise??????

and my previous ?.....do people just let their plants grow in 8-9 pH water even though the true pH of the 'still' not oxygenated solution would be the correct range??????

spurr · Nov 15, 2010

No, pH shouldn't rise if you bubble the water, unless something else is going on, like releasing of some Co2...

No one should try to use pH of 8-9 in hydro, that will make many soluble ions insoluble, esp. P and micro's, even if they are chelated (caveat: one chelate for P and Fe allows them to stay soluble in pH of ~8ish).

buddin_904 · Nov 15, 2010

ok so then whats the real answer....i enjoyed your post about co2 + water makes carbonic acid yielding a lower pH.....so your saying in my case CO2 must have been bubbled OUT of the water yeilding a higher pH value.....

sorry to keep asking questions but u seem cool...sooo whenever someone bubbles a solution WONT co2 bubble out???

you say pH shouldnt rise if its bubbled....so are you saying pH should drop?????
what happens???????

EDIT

what exactly will happen TO THE PH when you bubble a full spectrum nutrient solution at a current pH of 6.0 and at a constant temp of 75*.......thats what im meaning to ask

pH keeps climbing WTF?

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