PH Down - Why do I need so much for WELL water, but literally drops for RO

Just curious the science behind this question.

Ive been waterring with my personal well for years now. Starts @ 300 ppm and a PH of 7.3 right out of the ground. When making nutes for my waterring I usually need about 2.5ml / gallon of water of PH down to bring the PH to the 5.7-5.8 area.

I decided to try out some RO water since I got a jug for free and I was just starting some seedlings so I was just going to ph the water, it started at about 6.8ph right out of the bottle, about 3 gallons. I put in 5 *DROPS* of PH down, probably less than a single ML the the PH plummeted to the low 3's

My PH down is dutch nutrients 85% phosphoric acid. But I had to toss the water and just used regular well water instead.

Im just curious, is there something in the well water that stops the PH from going on such a freefall??

Ive always been to worried Im using to much PH down because when I mix a batch for the bigger girls in flower of 20 gallons I usually use about 10ml of PH down. My GH nutes only use about 30mL each.

The plants are "generally" ok and I dont nit pick about any problems and the plants all make it to the end. Just trying to refine a little bit and expand my knowledge. I dont think I will run RO water for my application but I would like to run it in my cloner and water my seedlings with it since I dont know the exact recipe of my well water ad what the plants are getting so young

Yeah I believe the harder the water the more it takes to change the ph.
It depends on what is in the water, tap water is buffered due to the calcium and magnesium amongst other things.
Well water may be naturally buffered in other ways but its basically what is in the water that makes the ph harder to adjust which is why RO changes so easily, because there is nothing to buffer it.

I wasn't sure if this was a serious question or not.

Ive just never used RO water before I suppose. I had no idea a literal single drop would suffice to bring the PH from high 6 to high 5 with literally a single drop for atleast 3 gallons of water.

Caused by carbonates in the water, more than likely calcium carbonate. My well has carbonates alone in the 300 ppm range.

RO water lacks the calcium carbonates and other minerals dissolved in your well water, which makes it far more susceptible to acidic shit like PH down. My water is like 330ppm's at like ph 7.9 or some shit, and I use about 12-14 ml of PH down in every 3.5g batch of nutes I mix, and that's with using a 50/50 mix of RO and well water.

"Don't worry about the pH of RO water; it is very difficult to accurately measure the pH of high-purity water, particularly with inexpensive, consumer-grade pH meters. They simply don't work well without some ions in the water.

Furthermore, the low concentration of dissolved solids means the pH can swing wildly when anything is added to it: there's no buffering capacity.

Once you add nutrients to the water, the pH probe will work better, and an accurate measurement can be made; the pH can then be adjusted to optimize growth."

Wilksey said:

RO water lacks the calcium carbonates and other minerals dissolved in your well water, which makes it far more susceptible to acidic shit like PH down. My water is like 330ppm's at like ph 7.9 or some shit, and I use about 12-14 ml of PH down in every 3.5g batch of nutes I mix, and that's with using a 50/50 mix of RO and well water.

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Jesus, you could spackle walls with that!

I assume someone explained how pH buffering works to the OP already. Cool cool, everybody had to learn it sometime. Definitely add nutes first then pH, or you will drive yourself nuts. I like to run pure RO occasionally, too.

I only use RO water. Our tap water comes out of a dugout on my property and sits around 300 now in the spring but goes up to and over 400 once the level goes down in late summer.

All full of farmer runoff and wh knows what else so we buy RO for drinking, cooking and my fast as hell still after 6 years BUNN coffee maker. Nothing but the best for my BUNN!

Good RO water has no real pH of it's own and should never be pH adjusted no matter what lies your pH pen is telling you.

Always add whatever you're going to feed your plants then check and adjust pH after a half hour or so once it's stabilized.

With hard water you should run a little experiment. Take a common volume of your water and test the pH with a freshly calibrated probe. Liter, quart or whatever you will usually work with.

Then adjust your pH to where you want it keeping track of how much it takes. Let it sit for at least 12 hours and test again. If it stayed the same then you know how much you need for that much water and can extrapolate to adjust larger or smaller volumes quicker.

If it has risen more than just a tenth or two then add more pH down until it's at your mark again and add that to what you put in before.

Keep doing that until it remains at the pH you adjust it to.

Phosphoric acid works great for plants but is a weak acid on the scale of acids. With water high in carbonates it will initially knock the pH down but is quickly exhausted so the left over carbonates will cause the pH to rise again and need more acid to knock it down. Eventually you will have added enough pH down to exhaust the carbonates and can suddenly find that you went way too low real fast as there was nothing left for the acid to react with.

That's what happened with the RO water There is nothing in it to react to acid or base so the littlest bit of either will move the pH a huge amount in comparison to tap water.

That's the basics but there is lots more to understanding pH and how to maintain it properly. I stick to RO and pH perfect nutes so I don't have to fart around with all that crap.

K.I.S.S. Keep It Simple Stoner!

Imo adding acid to a carbonate buffer seems pretty futile, i mean unless you hit waters ionization constant at ph4 lets face, its always going to rise back to the carbonates ph.

Personally id buy a fertilizer that buffered the water to where you need it and quit fighting an uphill battle, what most of us lazy ass growers who havent got time for non orofessional grow methods.

At 1ec your water should start obeying the buffer of nutrients in your ferts.

Theres keeping it simple or theres just doing the easy way and stop kidding yourself

I actually pH twice, once after the addition of K Silicate and again after all nutrients are mixed.

TurboTokes said:

Ive just never used RO water before I suppose. I had no idea a literal single drop would suffice to bring the PH from high 6 to high 5 with literally a single drop for atleast 3 gallons of water.

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The good thing is once you ph well water it stays stable at that ph forever it seems. Like you I use my well water for everything including hydro. Once I ph my rdwc setup it doesn’t move. It takes a bit more in the beginning but stays stable so pros and cons you know.

Lordhooha said:

The good thing is once you ph well water it stays stable at that ph forever it seems. Like you I use my well water for everything including hydro. Once I ph my rdwc setup it doesn’t move. It takes a bit more in the beginning but stays stable so pros and cons you know.

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Well water might have other ionic sruff in than carbonates.

Kingrow1 said:

Well water might have other ionic sruff in than carbonates.

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I get my well tested every year. Have to for my big ones I use on the fields.

jarvild said:

I actually pH twice, once after the addition of K Silicate and again after all nutrients are mixed.

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You pretty much have to with most silicate products. The pH can be over 10 and cause precipitation of some of the things in the nutes you add after it.

I'm using the Rhino Skin from AN and it only gets my RO water to 7.4 so it doesn't need to be adjusted before adding nutes. I'm using AN nutes too so it should all work together fine but the Rhino could be used with any brand of nutes and is Coco safe as well.

Lordhooha said:

I get my well tested every year. Have to for my big ones I use on the fields.

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I feel this is the main commercial idea, know your water.

Kingrow1 said:

I feel this is the main commercial idea, know your water.

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I did it just for my house before I had my others put in. It doesn’t cost much and given the fact that ground water changes it nice to know what your drinking

Kingrow1 said:

Imo adding acid to a carbonate buffer seems pretty futile, i mean unless you hit waters ionization constant at ph4 lets face, its always going to rise back to the carbonates ph.

Personally id buy a fertilizer that buffered the water to where you need it and quit fighting an uphill battle, what most of us lazy ass growers who havent got time for non orofessional grow methods.

At 1ec your water should start obeying the buffer of nutrients in your ferts.

Theres keeping it simple or theres just doing the easy way and stop kidding yourself

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A strong acid will easily break a carbonate buffer.

Silicates are so pointless.. How about feeding plants what they actually want. Crock nutrition... (still waiting to see what a silicon deficiency looks like)

So simple break it up 5050. Ro: well.. then ya have your bicarbonate buffers and or raise your micros form 5 mils to 8 mils to compensate.