Water chemistry question

[Mr.Juice]

So here’s the deal. Sick and tired of using RO water. It’s very wasteful for the system to make and then have to deal with CalMag issues when supplementing. I want to simplify things for myself

My water is very alkaline, live beside a limestone quarry, so lotsa of calcium carbonate. Lately I fill a 5 gal carboy and use an air pump and two stones to bubble constantly in between waterings. Before watering I would ph my water with 34% phosphoric acid.

So here is what led me to this post. For some reason I decided to put 10ml of 34% phosphoric acid into a full 23L carboy and then put in airstones to bubble. Now the water had turned cloudy.

Carbonic acid? Calcium phosphate? Or something else. I’m a biology and physics guy, so I’m not up to snuff with the chemistry of what’s going on here. If anyone could enlighten me it would be greatly appreciated.

 

[chemistry]

What's your PH in your 5 gallon carboy after you add 34% Phosphoric Acid? I add around 15ml to 5 gallons of water, that gives me a PH of 6.0, my water out the tap is 260ppm with a PH of 7.0

 

[Mr.Juice]

What's your PH in your 5 gallon carboy after you add 34% Phosphoric Acid? I add around 15ml to 5 gallons of water, that gives me a PH of 6.0, my water out the tap is 260ppm with a PH of 7.0

I just double tested both values.
Tap water: 426 ppm 7.6 pH

Carboy , Tap water + phosphoric acid + air-stone bubbling: 369 ppm 8.0 pH

Wtf? Lol

 

[chemistry]

Sheeeet. that is some hard water. If you mix your RO half and half with your tap, that should bring it down into the 200's. That should make your water near perfect to grow with.

 

[oldskol4evr]

mine is 7.24 ppm 315 out the tap,so i just figured it out with my 33 gal thrash can grow,i use the 8-16-36 feed,magnesium sulfate,calcuim nitrate,been fighting all spring and summer to get some thing to grow in it,i mix 33 gal at a time,my well is 500 ft deep and limestone base aqufier,so the rest of story hahah anyway i noticed that my water had a film on it looked like wax right,scrape off and next day same thing,so i change it and all over again,same thing it kinda look like the nitrate was seperating,at least that what i thought,i have to put it in warm water to disolve it before adding,so just asume it was it,well even doing that still had the issue,so aquaman suggested adding air to can i did and plant took off got about 2ft long and just quit growing,so checked agian same seperation,so dumped the stuff again,filled can with water and sitting in 100 plus weather the water came out to 7.5 PH,so i figured i could just ph down it right,then added all the nutes and checked the ppm and ph with them in it,PH was 7.8 and ppm was at 1200,so i added ph down to get to 6.0,all good,came out on the hour and check PH continue to rise,so i just kept ph down,im a soil guy so didnt know any thing about water,by the time i got that water to 6.0 at end of day i had put so much ph down in there the water looked just like yours,so to save the plant dumped it all scrub the can got 6 bottles of ro water like yours and filled it,checked ph it was 7 ppm was 05,added all the ferts and 60 ml of hydrogaurd and it has been sitting at 5.8 PH and 1027 ppm for 2 weeks sitting in the 100 plus sun with no problem.
im gonna try a half tap and ro water mix next time i start a plant to see if it will grow,but with just the well water and heat of day i was spiking at 8.5 no good for any plant

 

[Dirtbag]

Calcium phosphate cloud for sure. It's actually a good visual example of what happens when you mix too much calcium and phosphorus in the res.

As a test to verify, you could fill two small clear containers side by side and only add phosphoric acid to one of them.

 

[chemistry]

Have you tried using just the tap water and adding minimal amounts of nuits, I'll bet a couple of hundred PPM's are plant edible from your tap.

 

[Mr.Juice]

I just finished a grow and was using 100% RO. And using CalMag to supplement. For the last couple weeks I’ve been doing half and half RO to tap water. Think I will continue that for the whole grow.

I would bubble the water and would pH before watering. It’s just crazy how adding the phosphoric acid BEFORE the bubbling caused a precipitate. Explaining my drop in ppm. Now that it’s been left for a while I can see sediment on the bottom. It’s a very fine white sediment.

 

[oldskol4evr]

I just finished a grow and was using 100% RO. And using CalMag to supplement. For the last couple weeks I’ve been doing half and half RO to tap water. Think I will continue that for the whole grow.

I would bubble the water and would pH before watering. It’s just crazy how adding the phosphoric acid BEFORE the bubbling caused a precipitate. Explaining my drop in ppm. Now that it’s been left for a while I can see sediment on the bottom. It’s a very fine white sediment.

adding air does raise the ph,that might be the spike your having,i dont check my ph and ppm until all is made and adjust from there,guess im doing it wrong,without air my mix runs at 5.8 with air it's 6.0 to 6.2,when i get to 6.2 i add the hydroguard and the ph drops back around 5.9 to 6.0,once i started using the ro water ive had no more problems with any of it and as i mentioned i run the can outdoors in the blistering sun,no clue how warm water is,i just keep eye on the ph and ppm.
my well water is weird as shit,some times the water is as clear as glass ,when filter needs changed pressure slows and milky white water comes out the tap,the day i got all the smoky water i added quite a bit ph down and hell it looked like milk,so for the hydro stuff which i plan to grow melons and cucumbers all along my wall ro water,my container garden and ground garden gets well water and soil adjust and does fine with it,not the water plants i lost 3 difrent plants starting out,the can method is supose to be no pumps or air,i added air because of the smoky water and slime on roots,now i know it was just the well water,next plant set im gonna try ro water without the air and see if thats the trick in the method

 

[Dirtbag]

PH rises when you bubble air through nutrients because the Co2 reacts with stuff like calcium forming carbonates that raise ph.

 

[Mr.Juice]

Yeah, I will just go back to bubbling like normal then pHing after. It was just a weird situation that I didn’t expect.

Pretty sure it formed a precipitate of calcium phosphate. This is my best guess that happened.

Bubbling air (containing carbon dioxide) creates carbonic acid, the carbonic acid reacted with the carbonates in the water and in the presence of phosphoric acid resulted in a displacement reaction producing calcium phosphate precipitate. Not that this has any sort of practical application, I just found it pretty interesting exercise to figure out wtf was happening here. Or at least attempt to lol

 

[Krisforce]

Yeah, I will just go back to bubbling like normal then pHing after. It was just a weird situation that I didn’t expect.

Pretty sure it formed a precipitate of calcium phosphate. This is my best guess that happened.

Bubbling air (containing carbon dioxide) creates carbonic acid, the carbonic acid reacted with the carbonates in the water and in the presence of phosphoric acid resulted in a displacement reaction producing calcium phosphate precipitate. Not that this has any sort of practical application, I just found it pretty interesting exercise to figure out wtf was happening here. Or at least attempt to lol

Hy, how would you make a buffer solution with KHCO3 (Potassium bicarbonate) to have a pH of around 5,5–6. It would be used in a hydroponics system to make a buffer solution in RO water (demineralized) that can resist the acidic nutrient fertilizer. Tried with 60 mg/L and 90 mg/L of KHCO3, but unfortunately, the pH drops drastically to a level of pH 4 after 4-5 days, which is not good for my plants… IMPORTANT: the system is a passive system not bubbling CO2 in the solution!!!

So, in 1 L RO water, I added 90 mg of Potassium Bicarbonate (KHCO3) as a buffer and make the solution to 90 ppm (128,6 µS/cm). This brought the pH to 7,86. Then, after half an hour I added the Nutrient Solution. 935 µL Nutri Forte A (specification attached to the comment) + 935 µL Nutri Forte B (specification attached to the comment). I stirred it. At the moment the EC showed 1203 µS/cm (1,203 mS/cm) and pH was 7,13. I added 80 µL Phosphoric acid (H3PO4) to adjust the pH. I stirred it. The EC at the moment showed 1205 µS/cm (1,205 mS/cm) and pH was 5,56 on 23,8 ºC.

The solution is in a Jar, not touching any plant only under pure air. The values changes by days:

Day0 - EC 1205 µS/cm | pH 5,56 | 23,8 ºC

Day1 - EC 1220 µS/cm | pH 5,81 | 22,0 ºC

Day2 - EC 1238 µS/cm | pH 6,01 | 21,5 ºC

Day5 - EC 1360 µS/cm | pH 4,02 | 21,9 ºC

I am asking your help figuring out how can I solve this. Should I raise the KHCO3? If yes, what should be the overall amount? What could be the problem?