pH Down Doesn't Actually Work?

[Drivejunky95]

Hey all,

I'm growing in coco for my first grow, and I'm now discovering and reading about coco having issues with Cal/Mag due to the Cation Exchange Capacity, but........

I decided to do a simple experiment in regards to pH'd water because I noticed runoff pH was increasing and then capping at 6.5 - 6.6. This isn't ideal since plant nutrients are absorbed at different pH levels, and I'm noticing stunted plant growth after ruling out as many stunting factors as I possibly could.

Test group:
Tap Water (168 EC, 81 PPM)
Tap Water w/ pH Down
Tap Water w/ Cal/Mag
Tap Water w/ Flora Mirco Solution
Tap Water w/ completed flora series nutes, rooting, silica and wetting agent solution suitable for a late veg watering (no pH up/down added).

I tested the pH levels over a 48hr period. pH meter was re-calibrated in pH calibration solution before test started. Temperature of 68-70 F during each test, not enough to change the pH more than .01 pH.

Starting Tap Water: 8.0 pH
24hrs - 8.3 - 8.4 pH
48hrs - 8.5 pH

Starting Tap Water w/ pH Down: 6.4 pH
24hrs - 7.3 - 7.4 pH
48hrs - 7.7 pH

Starting Tap Water w/ Cal/Mag: 8.5 pH
24hrs - 8.1 pH
48hrs - 8.0 pH

Starting Tap Water w/ Flora Micro Solution: 8.0 pH
24hrs - 8.2 pH
48hrs - 8.1 pH

Starting Tap Water w/ Completed Nute Solution: 6.9 pH
24hrs - 7.5 pH
48hrs - 7.6 pH

One could argue that the tap water with pH down went up because the tap water pH went up, but the pH'd down water increased 1 pH in 24hrs compared to the tap water w/o pH down increasing 0.4 pH in 24hrs.

So to remedy this in a coco grow, (or hydroponic) one would want to constantly water to runoff 2-3x daily with correct pH, regardless of growth stage, just to keep the pH in check. But in addition to this, grows in soil would be subject to the increase in pH in pH'd down water as well.

Do you agree?

 

[fanleaf]

Hey all,

I'm growing in coco for my first grow, and I'm now discovering and reading about coco having issues with Cal/Mag due to the Cation Exchange Capacity, but........

I decided to do a simple experiment in regards to pH'd water because I noticed runoff pH was increasing and then capping at 6.5 - 6.6. This isn't ideal since plant nutrients are absorbed at different pH levels, and I'm noticing stunted plant growth after ruling out as many stunting factors as I possibly could.

Test group:
Tap Water (168 EC, 81 PPM)
Tap Water w/ pH Down
Tap Water w/ Cal/Mag
Tap Water w/ Flora Mirco Solution
Tap Water w/ completed flora series nutes, rooting, silica and wetting agent solution suitable for a late veg watering (no pH up/down added).

I tested the pH levels over a 48hr period. pH meter was re-calibrated in pH calibration solution before test started. Temperature of 68-70 F during each test, not enough to change the pH more than .01 pH.

Starting Tap Water: 8.0 pH
24hrs - 8.3 - 8.4 pH
48hrs - 8.5 pH

Starting Tap Water w/ pH Down: 6.4 pH
24hrs - 7.3 - 7.4 pH
48hrs - 7.7 pH

Starting Tap Water w/ Cal/Mag: 8.5 pH
24hrs - 8.1 pH
48hrs - 8.0 pH

Starting Tap Water w/ Flora Micro Solution: 8.0 pH
24hrs - 8.2 pH
48hrs - 8.1 pH

Starting Tap Water w/ Completed Nute Solution: 6.9 pH
24hrs - 7.5 pH
48hrs - 7.6 pH

One could argue that the tap water with pH down went up because the tap water pH went up, but the pH'd down water increased 1 pH in 24hrs compared to the tap water w/o pH down increasing 0.4 pH in 24hrs.

So to remedy this in a coco grow, (or hydroponic) one would want to constantly water to runoff 2-3x daily with correct pH, regardless of growth stage, just to keep the pH in check. But in addition to this, grows in soil would be subject to the increase in pH in pH'd down water as well.

Do you agree?

Your tap water seems to be strongly buffered as mine is.
I can let a bucket of my tap water sit out for a day and check the pH and it will be eight. Then I can add pH down to bring it down to 6.5 and all looks well until I let the bucket sit for about 4 hours and it's back at 8 again. I have added PH down to my tap water about six times over the course of a week and it kept climbing back up to eight every time. It took a week for the pH to stay at 6.5. I can't tell you how much acid I added to the water during that week before the water finally gave up and left the pH at 6.5. Shortly thereafter I bought a reverse osmosis kit and have never looked back. My water is now 0 - 2 PPM and pH neutral.

 

[Chris Scorpio]

Some tap water is extremely saturated with many many stuffs

Mine has a ppm of 400-550

As stated by Fanleaf I'm sure yer has lots of buffers thus the changes

pH up and down work great, but the medium used in will impact it greatly

 

[Drivejunky95]

Wow... finally the answer to everything revealed. An RO system, okay!

 

[fanleaf]

Wow... finally the answer to everything revealed. An RO system, okay!

Yes, there are table top units that are under $100 and some really good ones that have a much greater water making capacity per day for around a $150. For me it was the best investment I have made and has taken care of all of my water problems 4 years now. All I've had to do is change the filters once or twice a year but those are cheap.

 

[Drivejunky95]

Can't tell ya'll how revealed I am in hearing this. I'll be getting an RO system. Ya'll are aces. Thank you.

 

[Chris Scorpio]

I have an RO Buddy, was like $50, works great

 

[Barney86]

Mix you're nutrients then ph the final mix mate.

 

[fanleaf]

Mix you're nutrients then ph the final mix mate.

I think you missed the point and the majority of the conversation.

 

[Dusted]

pH down is usually a 5% phosphoric acid solution. I use a 75% active acid since my water has such high tds and pH. It gets expensive using commercial pH down

 

[fanleaf]

pH down is usually a 5% phosphoric acid solution. I use a 75% active acid since my water has such high tds and pH. It gets expensive using commercial pH down

Very true, it's way cheaper and even better usually to just use new battery acid for pH down. I have Muriatic, Sulfuric, Nitric and a few others on hand. Sodium Hydroxide is a VERY potent pH up. Be very careful with any of these though. Especially the Nitric and the base-Sodium Hydroxide. Lye is as dangerous or more than most acids.

 

[Dusted]

Very true, it's way cheaper and even better usually to just use new battery acid for pH down. I have Muriatic, Sulfuric, Nitric and a few others on hand. Sodium Hydroxide is a VERY potent pH up. Be very careful with any of these though. Especially the Nitric and the base-Sodium Hydroxide. Lye is as dangerous or more than most acids.

Only use phosphoric acid! It is the P in nutrients. The rest will poison your plants, except the Nitric which is the N in nutrients

 

[PE636]

I have been having good luck with the Cyco platinum ph down. I think it's 47 percent phosphoric acid.

 

[fanleaf]

Only use phosphoric acid! It is the P in nutrients. The rest will poison your plants

Not even close. Sorry but sulfuric is probably the cleanest. None of then will harm the plants man. What on earth would make you think that?

 

[fanleaf]

Very true, it's way cheaper and even better usually to just use new battery acid for pH down. I have Muriatic, Sulfuric, Nitric and a few others on hand. Sodium Hydroxide is a VERY potent pH up. Be very careful with any of these though. Especially the Nitric and the base-Sodium Hydroxide. Lye is as dangerous or more than most acids.

Only use phosphoric acid! It is the P in nutrients. The rest will poison your plants, except the Nitric which is the N in nutrients

Perhaps if @Emilya feels inclined to weigh in here she could. Someone with a bit more chemistry knowledge. I don't think any of them would "poison" the plants in the tiny amounts used for pH. You can get Sulfuric from any auto parts store for under $10 and have tons and tons of pH down.

 

[Growingasmile]

Your tap water seems to be strongly buffered as mine is.
I can let a bucket of my tap water sit out for a day and check the pH and it will be eight. Then I can add pH down to bring it down to 6.5 and all looks well until I let the bucket sit for about 4 hours and it's back at 8 again. I have added PH down to my tap water about six times over the course of a week and it kept climbing back up to eight every time. It took a week for the pH to stay at 6.5. I can't tell you how much acid I added to the water during that week before the water finally gave up and left the pH at 6.5. Shortly thereafter I bought a reverse osmosis kit and have never looked back. My water is now 0 - 2 PPM and pH neutral.

and some units are only 50$

 

[fanleaf]

and some units are only 50$

Very true. I started with one of those and it served me very well too. I'm now at a 200GPD unit that was $140 just because I go through so much RO water. I always keep a 20 gallon drum full and bubbling.

 

[TorturedSoul]

I think my pH Down is food grade phosphoric acid and my pH Up is a mixture of potassium hydroxide and potassium carbonate. I've seen warnings for years that stated pH adjustment may be difficult with "poor quality" water. And, specifically with pH Up (I don't remember in regards to pH Down), that I may need to use more product with "hard water." I've always assumed this was because of the presence of calcium carbonate and/or calcium bicarbonate / calcite. Not exactly highly water soluble (AFAIK) - but acidifying the solution (IOW, adding pH Down) will tend to dissolve at least some of it, thereby releasing CO₂. This action might(?) make the calcium more accessible to plants, but the CO₂ might(?) then react with some of the nutrients we have added. I don't (specifically) know.

This isn't exactly rocket science, lol, and the little bit of basic chemistry education we received in junior high school or before would be enough to understand the stuff - but it's probably on the list of 32.768 things that we assumed we'd never have to remember in our day to day lives and, therefore, didn't. I (vaguely ) remember having to balance chemical equations / etc. when I was 11 or 12 and it was easy, just simple math really. The real problem is probably that we often don't really know exactly what is in our nutrient bottles (and in what form), along with the fact that, for a lot of people, exactly what comes out of their tap when they turn the handle can change somewhat over the course of the year. Those of us who are on a municipal water supply (at least in the USA) should receive a water quality report once per year, but that's sort of a static picture of a dynamic thing, so to speak (although I wouldn't expect huge changes, again there could be some throughout the year).

BtW, typing "how to balance chemical equations" into a web-search engine got me 31,000,000 results. Videos, worksheets, articles/webpages that included the word "easy" in their title, et cetera.

I'm growing in coco for my first grow

I - and most folks, as far as I know - consider that to be a hydroponic media. What is your general target pH when mixing your nutrient solution, 5.8?

I'm now discovering and reading about coco having issues with Cal/Mag due to the Cation Exchange Capacity

I don't consider such to be "issues," more like that it's merely one of the product's traits that users need to be aware of. IMHO, it's the not knowing that tends to cause the "issues." By the way, you've probably read and/or been told to thoroughly hydrate your coco coir media and then rinse, rinse, and rinse it some more? Afterwards, soaking it in a mild calcium nitrate solution - optional but probably a good idea: also add magnesium to the solution - can help prepare it, as the calcium and magnesium ions will take the place of the sodium and potassium ions in the coco coir. Never allowing your coco coir to dry out at any time between prepping the stuff and harvest day is probably pretty important, too.

Just being exposed to air causes a slight(?) change to water's pH over time. There is CO₂ in our air, and it easily dissolves in water - which is probably one of the reasons that distilled zero-PPM water isn't, shortly after opening the jug for the first time.

I see that you have (I assume) General Hydroponics three-part Flora series, cal/mag a product that contains both calcium & magnesium, and a silica supplement. As far as I know, the proper order for adding these things is silica supplement, calcium & magnesium supplement, and then the three Flora components (starting with the Micro) as and when needed, making sure to thoroughly mix (hopefully, until dissolved!) after each addition.

What's in your wetting agent? Some kind of surfactant, I assume, but do you know its specific ingredient(s)?

You may already know this, and it's probably not relevant to your test results, but unless your pH meter and all the electric devices in/near your grow room are well shielded (which might be effectively zero percent of the stuff sold to cannabis growers ), those devices being powered up might influence your pH meter's results. Therefore, if you ever think your meter might be giving you "wonky" results - or are just curious - try unplugging or shutting down all your grow lights, timers, fans, pumps, etc. (and doing the same with nearby televisions/stereos/computers/home lighting/etc. might be useful, too), and then retesting the same sample to see whether your result changes. This is something that we should all probably do at least once, and again if we add another electric device to the general area, IMHO.

 

[Big Sur]

Avoid anything with sodium in it to add to your water. Many items called "PH Down" are for hot tubs and pools and they are sodium based (typically sodium bisulphate). Do not use this stuff. Sodium fools plants into thinking they have taken up enough water, when in fact they have not, and they will wither. For the most part, sulfuric acid is what large ag companies and golf courses use to acidify water with for plants. Several products also called "PH Down" are designed for fish tanks, and they are OK for plants, as they are also sulfuric acid based.

 

[Drivejunky95]

I'll be honest, I'm in veg while I absorb all this information until I can flower a response.