PH A Basic explanation

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dirtyoldman

dirtyoldman

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Depends on the media. pH is a tricky thing for a lot of growers, new and seasoned. In soil, pH of input solution is a damn near irrelevant if the soil is built properly. In hydro, you gotta have adequate alkalinity or keeping the solution from swinging like crazy is going to drive you insane.

If pH is diving in hydro, you've bad bacterial cultures blooming. It's a symptom of a deeper problem. pH should be pretty damn stable, on move on a smooth curve as EC and water levels change.

Distilled water could be used, but it's inadvisable since it's zero PPM. Even RO is pretty low but it still tends to have some EC in it, even if it's not terribly significant. You'll just have to use more alkaline buffering and distilled water just isn't economical for long term use.
It's why I haven't messed with hydro in 25 years. Too damned much fiddling around. And too easy to screw up. The only thing I need to pay attention to right now is to let the tap water sit for awhile to let the chlorine perc out of it because I definitely don't want that driving the ph down. Because although I'm rural my water still comes from a treatment plant. That's it. Done and done. And the plants do beautiful. I admire coco noir, but I know I'll probably be messing around with constant testing if I used it. In an end of the world survival scenario novel I'm working on coco-noir is the bomb in the bunker. Compressed like blocks and not taking up space after the apocalypse. The scrap and root bundles can be fed to earthworms which in turn can be fed to chickens.
 
dbrzz

dbrzz

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OK I'm going to do my best to explain PH since its something that is for the most part greatly misunderstood and can be confusing to new growers and even experienced growers alike. This will explain why we need both ppm and PH meters to give us informed information about PH

This will be a simple guide leaving out a lot of information. So lets get started with a couple of definitions to help you understand.

What is PH?​


PH is a measurement of how alkaline or acid a solution is based on measuring hydrogen ions. It tells us nothing more than the ratio of acidic to alkaline elements. It does not tell us how much of each the solution contains or the alkalinity of the water.

What is alkalinity?​


Alkalinity is the measurement of the waters buffering capacity (ability to neutralize acids). Its the total amount of carbonate and bicarbonate in the water that affects its ability to resist change to PH. If you know the alkalinity you can actually calculate the amount of acid of varying types needed to reach your target PH but we wont get into that.


So now we have a basic understanding of the difference lets get into some examples of source water and how alkalinity will affect PH.

RO and Distilled water​


Ro and Distilled water is very low in mineral content containing carbonate or bicarbonate sources, we know this because if we test the ppm its usually under 40 and as low as 0ppm. This means it has a very low alkalinity (ability to neutralize acids) and is easily influenced by anything added that's acidic. But likewise it does not contain acid and is easily influenced by anything added that's basic. This results in a very unstable PH that can be easily influenced by anything added or anything its added to. In hydro the ideal ppm of carbonate/bicarbonate sources to provide an adequate buffer will be 50-100ppm with 75ppm being the target. Less than this and PH may swing to fast and be unstable, more and it will not drift enough and will require too much acid that could affect nutrient ratio's negatively depending on the acid used. By adding alkalinity and then acid we provide a more stable PH because adding more of either will have less impact on the overall ratio of acidic to basic elements

When used in hydro it should have alkalinity (a buffer) added back to prevent wild PH swings. Any source of carbonates, bicarbonates, silicates or hydroxides will work to create alkalinity. Sources i would recommend would be calcium carbonate, potassium bicarbonate (commonly sold as PH up) and finally what i would consider the best option is potassium silicate as it is a source of potassium and silica which are both excellent for cannabis. When using RO or distilled you will want to add back some calcium and magnesium if your nutrients are not designed for RO/distilled water as that's usually what Ro filters are removing for the majority. But most cal/mag is in the form of nitrate and provides no alkalinity (buffering capacity) so adding one of the previously mentioned or other is still a must.

When used in soil this unstable PH is actually IMO beneficial if you have a pre buffered soil (which you should) This means the water will have no impact on the PH potential (more on this later) of the soil and will almost instantly be influenced by the soil to the take on the PH of the soil makeup. This is why i feel we do not need to be PHing our nutrient solution for soil grows (unlike soiless and hydro). The soil is what will adjust the PH of our nutrient solution.

Tap Water​


OK we all know tap water varies a lot form place to place and I will explain the basics of how to determine if your tap water is suitable or not for use. First we want the PPM and second we want the makeup of that ppm if available. Generally speaking the majority of the PPM makeup will be calcium carbonate. This is used to buffer the water supply and prevent acidic conditions that erode the coatings and will break down piping and leach them into the water supply such a lead (Flint Michigan ring a bell?) So we can generally assume the majority of the PPM in tap water is likely calcium carbonate but also some others like magnesium, sulfur, phospahte, iron etc. So if you have a ppm of 100-200ppm you can assume roughly 50-75% of that is calcium carbonate. Remember our target is 75ppm carbonate/bicarbonate sources to provide an ideal alkalinity (hope we are starting to see how import alkalinity is and we can't just go by PH) Now there are some cases when some sodium may be used such as sodium bicarbonate aka baking soda (can also be used as a buffer in a pinch but not recommended as a long term option) so we can google our local water report and see the makeup of the ppm in the water.

Soil PH potential​


Now when we buy a prebufferd soil like most of the ones we use they come "Prebuffered" (alkalinity adjusted) what does this mean? This means the company has added amendments that when water is added the resulting PH of the water in the soil will be in a favorable range for growing our plants. Often times peat is used to lower PH and lime is used to raise PH in these soils. Just like in water we want to control the alkalinity (buffering capacity) of the soil to have a stable PH that is not easily influenced by adding things such as nutrients or other. Unlike hydro and soiless where we control the alkalinity (buffering capacity) of the water by adding it directly to the water it is applied to the soil. Which brings me back to my point of we don't need to PH our nutrient solution in soil because the soil provides the buffering and will adjust the PH. Now things like lime and peat break down slowly over time and only soluble elements will impact PH so this is how they control the PH in soil over long periods of time, because it breaks down slowly and only a small amount is soluble at a time its unlikely after a grow it has been depleted. But if we are reusing the soil we should be looking at re amending the buffering capacity before using again to ensure there is enough to last through the next grow. Often times farmers will do this once a year before seeding crops.

Effects of nutrients and source water on PH​


First the PH down acids we use tend to break down much faster than the alkaline sources we use in both hydro and soil. For this reason we see a hydro systems PH generally rise over time unless something is creating more acid like decaying roots in which case we may actually see PH going down. Typically a PH increase of 0.2 in a 24 hr period is desirable and by adjusting the alkalinity we can control the PH drift. In the case of soil the acids used to bring PH down before feeding break down quickly and the alkaline and acidic buffer we have created minimizes the impact so they are really of not much benefit and have virtually no impact on long term PH potential of the soil. This is why we can't use them to lower high soil PH once we have an alkaline source buildup. However in hydro and coco PHing the nutrient solution is important because unlike soil there is not an adequate buffer established although in coco it is possible to do so.

Generally speaking the ratio's of nutrients we use will be acidic so when we get a buildup of nutrients we will almost always see PH drop. This is where you often hear ppl say flush the media. What this does is dilutes the dissolved elements and will remove some from the media in runoff.

Conversely a water source with high alkalinity can build up in the media and cause the PH potential of the soil to rise over time and in turn the PH of the water added to it. This is the reason we should look at the alkalinity of the water source not the PH as PH cannot measure the potential influence but rather only result.

Often in both circumstances its a good idea to flush the media to remove excess amount of available elements that may be affecting the PH negatively.

I'm gonna stop there and if anyone has questions i will do my best to answer them. If you have something you would like to add please do.


Aqua Man
Excellent information and explanation. I found an excellent Cal/mag product for buffering your coco. Its from TPS nutrients called Organic CalMag OAC. 4.5% calcium 1.1% magnesium, derived from calcium carbonate and calcium magnesium carbonate.
Cheers!
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Baywe

Baywe

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How is my tap water? I know its hard water since we have build up but I've been watering with tap water for my very first grow. I'm growing in 50%promix 30% perlite and 20% EWC. Top dressing with gaia green.
 
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Baywe

Baywe

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Also this thread is great for newbies such as myself, sometimes I get overwhelmed with all the information there is to learn about growing in general but it's crazy fun to grow your own plants.
 
Aqua Man

Aqua Man

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How is my tap water? I know its hard water since we have build up but I've been watering with tap water for my very first grow.
I dont see values for sodium but the rest looks good. Fairly high in sulfur which is a nice bonus. Im not familiar with 2-4-D acceptable levels but i would guess its not an issue at those level’s although its not something you like to see in your water.

Its pretty hard water so depending what style of grow you use it could be a benefit but could be an issue in a smaller container soil or peat grow over a longer period.

The concern i would have is what is the source of the CaCo3. Try to locate the sodium levels to make sure its not sodium bicarbonate. You want sodium levels well below 20ppm and the lower the better. At 20ppm or over i would cut it with RO or just use RO period
 
Aqua Man

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Also this thread is great for newbies such as myself, sometimes I get overwhelmed with all the information there is to learn about growing in general but it's crazy fun to grow your own plants.
Yeah there is a lot to learn to become proficient and maximize things but thankfully enough there is enough room for error to not have to start perfect which allows you time to learn and improve over years
 
Baywe

Baywe

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I dont see values for sodium but the rest looks good. Fairly high in sulfur which is a nice bonus. Im not familiar with 2-4-D acceptable levels but i would guess its not an issue at those level’s although its not something you like to see in your water.

Its pretty hard water so depending what style of grow you use it could be a benefit but could be an issue in a smaller container soil or peat grow over a longer period.

The concern i would have is what is the source of the CaCo3. Try to locate the sodium levels to make sure its not sodium bicarbonate. You want sodium levels well below 20ppm and the lower the better. At 20ppm or over i would cut it with RO or just use RO period
Yes, let me browse thru 23 pages and pretend to know what im looking for 🤣 one moment please.
 
dbrzz

dbrzz

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How is my tap water? I know its hard water since we have build up but I've been watering with tap water for my very first grow. I'm growing in 50%promix 30% perlite and 20% EWC. Top dressing with gaia green.
Actually your water is pretty good. My tap is 800-1200 ppm calcium carbonate/ magnesium carbonate. Hard water to the extreme.
 
Baywe

Baywe

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Yup your good to go with that… what syle of grow are you doing?
50% Promix organic 30% perlite and 20% EWC. Top dress with gaia 444 and 284. I struggled with watering in the seedling stage, figured that out then heat/light stress since leaves started to taco so had to work on my vpd. I haven't ph'd my run off the entire grow but after reading this thread i should probably get on it.
 
Baywe

Baywe

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Actually your water is pretty good. My tap is 800-1200 ppm calcium carbonate/ magnesium carbonate. Hard water to the extreme.
Damn you have a water softener installed? I have to descale my humidifier after every winter with white vinegar and other things like coffee maker and what not so i don't have to keep buying new.
 
Aqua Man

Aqua Man

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50% Promix organic 30% perlite and 20% EWC. Top dress with gaia 444 and 284. I struggled with watering in the seedling stage, figured that out then heat/light stress since leaves started to taco so had to work on my vpd. I haven't ph'd my run off the entire grow but after reading this thread i should probably get on it.
Just good to keep an eye in to see if you need to adjust anything. Dont bother PH adjusting your nutrients. If the runoff starts to creep up to much just add a little aluminum sulfate to your soil ut you should be fine
 
Baywe

Baywe

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Just good to keep an eye in to see if you need to adjust anything. Dont bother PH adjusting your nutrients. If the runoff starts to creep up to much just add a little aluminum sulfate to your soil ut you should be fine
Thanks for the advice.My wife has one of those aquarium ph drop test package which is collecting dust so I’ll put it to good use 😁
 
Frostie069

Frostie069

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Wow another great thread.

@Aqua Man, any chance you can evaluate my h20 bro?

All I know is it just wants to stay up around that 7.7 bit higher and sometimes a little lower( it doesn't fluctuate). So my alkalinity must be high because my water continuously is buffering out my acids? ph down can not keep it down
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Aqua Man

Aqua Man

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Wow another great thread.

@Aqua Man, any chance you can evaluate my h20 bro?

All I know is it just wants to stay up around that 7.7 bit higher and sometimes a little lower( it doesn't fluctuate). So my alkalinity must be high because my water continuously is buffering out my acids? ph down can not keep it down
View attachment 1267607 View attachment 1267609 View attachment 1267608 View attachment 1267610
Looks ok chloride a bit high bit hardness looks fine.

What source of PH down are you using? Possibly citric acid?
 
Aqua Man

Aqua Man

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try and get my hands on some food grade phosphoric acid?
Yea thats why your ph is not stable… citric acid reacts with bicarbonate to produce carbonic acid and then is off gasses as co2. Thats why citric acid will not work for hydro no matter what the bottke or hydro store guys say to you… its not good for hydro
 
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