However, sulfuric acid is the go to PH down in virtually all commercial grows - mainly for the cost. So if you are eating any hydroponically grown vegies, even organic ones, they were almost certainly grown with battery acid
The PH Down that you buy in bottles is phosphoric acid, which is no safer/better - or worse - than sulfuric acid. You can also buy phosphoric acid in bulk far cheaper than PH Down, but its still more $$ than sulfuric.
Yes, I did try vinegar, but didnt like it at all. It took tons of it to make any PH changes and it didnt hold well at all. Plus, it degrades as it ages after the bottles are opened. From my reading, sulfuric acid is supposed to hold the PH slightly better than phosphoric acid, and for me, it works way way better than vinegar.
But I understand how you feel. I was the same way when I first read about people using H2SO4 - but I got over it
Very interesting article!! It explains @MicroDoser 's PH rebound and slow stabilization perfectly. It also explains my slow raise in PH in the rez.
Factors which accelerate off-gassing (and speed pH rebound) include higher water temperatures, increased circulation, and especially increased aeration.
The routine (popularized online by Ben Powell) involves adding just enough acid to lower the pH to 7.2, and then circulating and aerating the water as much as possible. The acid lowers the alkalinity, and the aeration accelerates the process of CO2 off gassing, thereby increasing the pH. Then more acid may be added, to pH 7.2, and so on â until the alkalinity reaches the desired target. In a relatively short period of time (at least, compared to traditional methods) the target alkalinity is reached without a) taking a lot of time, or b) allowing the pH to drop below safe and desirable ranges.
However, Im not sure how that relates to or explains why my tap water goes up in PH? There was NO acid added in my tests. This was straight tap/well water, and as far as I know, it is not treated in any way. Although, I could be wrong about that come to think of it. The well is inspected by the county every so often and it is managed/maintained by a private company. Guess I need to make some calls tomorrowâŠ
I would have expected the aeration I was doing to speed up the equalization of the dissolved CO2 already in the water and atmospheric CO2. On the other hand, that assumes the well water starts out with a more or less ânormalâ concentration of dissolved CO2 - something else I dont know.
@anon32470837,
I am no chemist, but perhaps there is enough dissolved material in your tap water to have the carbonic acid/carbonate/co2 offgassing happen?
I would rinse the airstone and all test materials in distilled water, and try with distilled water under the same conditions. In fact I was going to try just this experiment, but dropped and busted my bluelab probe no more than 30 minutes ago. Will pick up a replacement tomorrow if i have time and give it a shot.
I have not experienced said nonlinearities. Where i live the tap water is pretty much rain water ph6.9 and 10ppm tds. But curious as well. Hope the hive mind figures it out.
Brilliant idea for a test! I can do that nowâŠand yeah, I was just starting to wonder the same thing. My tap water varies from around 80 PPM up to 200 at times. At the moment its right at 100. I would think that would be too low to cause this type of issue but maybe the carbonic acid doesnt show up on an EC test? I have no clue.
Well, crap. This may not work as well as I hoped. This is a quote from the manual for my PH meter:
This pH probe will NOT give accurate and stable readings for distilled or deionized water.
This is because distilled and deionized water do not have enough ions present for the
electrode to function properly. Specialized pH probes need to be used for
distilled/deionized water measurement
I just tried to test the PH of my WalMart distilled water and its all over the place. Started out at 8.4 and drifted down to almost 6. Took it out and put it back in and it started at 8.0 then went to 7.1 then to 7.9 then to 6.1 over the next 5 minutes.
Im going to do the test anyway and see what happensâŠ
HCO3 2- is calcium bicarbonate.
CO3 2- are carbonate ions.
H2C03 is carbonic acid (derived from CO2 in solution).
Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.
CaCO3 + CO2 + H2O â Ca(HCO3)2
This reaction is important in the erosion of carbonate rock, forming caverns, and leads to hard water in many regions.
Alkalinity is the base neutralizing or âbufferingâ capacity of water (i.e., ability to neutralize acids). Total alkalinity is a measure of the net effect of all cations and anions; however, it is typically approximated by carbon dioxide (CO2(g) and CO2(aq)), carbonic acid (H2CO3), bicarbonate (HCO3), carbonate (CO3), and hydrogen ion (H+). These species make up the âcarbonate system,â one of the most important acid-base relationships in aquatic systems. [1]
Aeration causes CO2 to outgas. So aqueous CO2 becomes gas CO2 and leaves the water: CO2 (aq)->CO2 (gas)
Carbonic acid (H2CO3) in the water then creates CO2 according to this reaction: H2CO3 ->CO2 + H2O
Bicarbonate (HCO3â) in the water creates carbonic acid (H2CO3) according to this: HCO3â + H±>H2CO3
Net result: H+ is consumed and pH goes up â alkalinity does not increase
If you are going to talk to whomever maintains the well, ask if they have a recent test on the effluent particularly the hardness. If itâs a town supply, they are probably required to keep water testing records. Do you have lime scale on your taps? Or, maybe itâs time to send out a sample for analysis?
This would explain Larryâs nonlinearity - early hydronium introduction has a marginal effect because various carbon compounds gobble up all the H+. Then a tiny bit is enough to send PH way up.
Well crap again. That article explains @MicroDoser 's PH rebound and slow stabilization and my slow raise in PH in the rez. In my case, I tend to aerate very strongly - water falls and lots of bubbling.
The problem with this new knowledge, is that it complicates one of my favorite ârules of thumbâ for monitoring EC levels in the rez.
EC goes up and or PH goes down, lower EC
EC goes down and PH goes up, consider raising EC
If the PH is always going to go up when I aerate, then how am I going to know if the change in PH is because of the plants using the nutes, or the aeration changing the chemical balance in the water, or the PH rebound after adding acid?
(sigh) I guess Im going to have to do more testing with just tap water to determine the rate of change due to aeration, THEN do another series to see how fast the rebound is. I need to establish those two before I can know if its the plants causing the change or the system.
Sometimes just a little knowledge is a good thing as far as confidence and happyness and more causes extra work!
Hereâs something I found for that experiment @anon32470837
As long as it has not had any contact with air (particularly CO2), deionized water should have a conductivity of 0.055 uS/cm, or a resistivity of 18 megohms at 25 °C 5,47. If the deionized water has equilibrated with air, the conductivity will be closer to 1 uS/cm (1 megohm) at 25 °C (and it will have a pH of 5.56). Most standards allow for a conductivity range of 0.5-3 uS/cm at 25 °C for distilled water, depending on the length of time it has been exposed to air
LOL we must think alike I was just reading a similar article about the same thing. According to this one, the PH of distilled water will change - potentially a lot - as soon as it is in contact with air and begins to dissolve CO2. It could go as low as 4 from what they said.
The bottle I used has been open for several days. I use it as the rinse for my PH probe between readings.
The distilled water test has been bubbling for about an hour so far and the PH readings are still all over the place. Im going to let it run longer, but this is starting to look like its my water that is the problem. It must have some serious crap in it
Wow, wish my tap water was so clear of contaminants.
Even more wow, I donât get this low using ROâŠ
From a single data stream from a PH sensor there is no way of knowing. If two situations have the same effect on PH then just reading the PH does not give you enough info to figure out which effect you are seeing. You would need to have a note of how your plants did last cycle, what the feed strength was, and what your PH was doing at the time to really know. I just lock down the PH to 5.8-5.9 (never over, never under) and apply the same strength feed these days, the plants take what they want and as long as I do a tank change every few weeks they have a good balance of what they need. I am going lower and lower on the nute strength and the yield and quality is going up and up. This time I will not be going over 500ppm (580 last time)
To my mind the wild variation shows how little crap you have in your water. When you have a lot of crap it takes a lot of other crap to change it. Hardly any crap means a little extra crap will change it a lot. Personally when using RO, I will usually put in some PH up and some PH down and some calmag to act as a buffer for the water. I find the PH is much more stable after that.
Very interesting thread, I like threads like this that explore a concept. There is usually something new and interesting to discover.
EDIT :
Just looking at that link
After adding acid to the pool water, the pH goes down (at first) because of the effect on pH of the increasing amount of CO2 (aq) produced by the acid. Shortly afterwards, the pH begins to rebound and eventually can return to its original level
and this is what I find. I am curious to discover what causes the settle at the end though, I had a look but did not see anything that would explain it.
Not sure about that either. Could be your water has something else in it, but I have no clue really.
Well, Im convinced its my water and not the tubing, stainless bolt, or the air pump. The distilled water shows no changes after 24 hours.
I tried reducing the aeration in my rez, but Im not sure that did anything or not. The PH seemed to maybe go up a bit slower, but I havent documented it closely enough to tell for sure. I dont want to give up or reduce the aeration, so I will jsut have to live with the PH swings and adjustments for now.
This is pushing me more towards trying out an HP Aero or AA aero system though. I can do drain to waste with both of those and reduce my nute use at the same time in addition to not having to monitor EC or PH over time and no aeration of the rez needed. Start up costs are high thoughâŠ
Oh - the county water quality office does not believe in answering their phones and the voice mail system isnt working properly. I will have to try again on Monday. The water management company took a message and promised me that the âaccount managerâ would call me back, but no callâŠ
Yea, they shouldnât really need to know that information unless youâre asking for their advice. If anything, âIâve been having problems with my salt water aquarium chemistryâŠâ
