RO water - cal mag experiment

The Culligan R/O machine at Walmart is putting out 45ppm water so I finally got an R/O machine of my own. It is making 2ppm water so I am looking forward to try it out in a true living organics grow. I am running into calmag issues of course but before I run out and buy calmag+ I'm hoping I can try to dissolve dolomite lime for calmag and blackstrap molasses for iron and more calmag. I am working with a pH tester (drops), PPM meter, and pulverized dolomite lime. I need to get a GH/KH test kit but haven't got around to that yet.

Update: OK came a long way it was taking 5 days to get 80 ppm water and now 100 ppm water in 5 hours using carbonic acid from exhaling. Thanks to Verdant Green's citric acid thread and spurr/mr fista's chemistry it looks like food grade citric would be an even quicker and easier method of dissolving the lime. Another thing that helped was using pulverized dolomite lime instead of pelletized. The pelletized needs to be rinsed which is a pita and it dissolves more slowly than pulverized because it has much larger granules. The upside of pelletized is that it settles out almost immediately while the pulverized stays in suspension for hours.

The most helpful thing I learned from my sloppy science method is that holding your breath helps a ton. Apparently normal breath is 30,000-40,000 ppm CO2 but if you hold it for 60 seconds it becomes 80,000 ppm (8%). For whatever reason the 80,000 ppm air works 10X better at dissolving CO2 into the water.

So exhaling will get the job done in a pinch but I think citric acid is a more realistic solution long term. Anyway the girls really love this water. I tried it at 80 ppm, 100ppm and 120ppm so far. The soil was depleted so I have no real idea what the right level is long term. Once I get the GH/KH kit maybe I can figure out how much actual calmag is in there and if there are any carbonates.

From what i can tell the cutting edge cal amp that i use is only calcium chloride. Im about to do a side by side run with the ces amps and epsom/cal chloride. Let us know how yours works out.

Also I think carl carlson has a good tread on this subject.

Thanks I will look for the thread from CC.

Ehow has some info about pond water:

-Soften Water
Peat moss contains humic acid as well as tannic acid. Humic acid is a product of humus, partially or fully decayed organic vegetable or animal matter used by plants as a nutrient. When you add peat to hard water (water with high levels of minerals), the negatively charged humic acid molecules bind with both positively charged magnesium and calcium ions, removing these minerals from the water and thereby softening it.

-Lower pH
When molecules of humic acid bond with magnesium and calcium, the minerals release free positively charged hydrogen into the water, lowering the pH and thereby making the water acidic.

SupraSPL said:

So I tried 800ml of R/O + 200ml of rinsed pelletized lime. The R/O started off at 4ppm and jumped to 16ppm when I added the (imperfectly) rinsed lime.

-R/O starting ph=6.3 TDS=4 ppm
-added 200ml rinsed lime ph=6.7 TDS=16 ppm
+2 hours 25ppm
+2 hours 30ppm ph=7.2
+12 hours 34ppm
+22 hours 40ppm
+24 hours 44ppm
+13 hours 47ppm ph=7.2

There should be plenty of Ca and Mg dissolving. Hopefully this water has enough to avoid using calmag plus. It would be easier and cheaper to just keep a pile of dolomite in the bottom of the R/O jug. A pinch of Epsom for sulphate and maybe iron can come from the molasses.

Click to expand...

Very interesting experiment.

desertsquirrel said:

From what i can tell the cutting edge cal amp that i use is only calcium chloride. Im about to do a side by side run with the ces amps and epsom/cal chloride. Let us know how yours works out.

Also I think carl carlson has a good tread on this subject.

Click to expand...

on what subject?

Yes, the CES Plant Amp is Calcium Chloride

using RO is not ideal if the tap water has good level of alkalinity (i.e. < 100 ppm, ideally 40-60 ppm is best), and if tap water isn't hard. It's good to have low level of alkalinity in water to keep pH in soil solution from dropping too much (microbe exudates play a huge role in the pH of the soil solution and rhizophere, as does exudates of roots, which are acidic and basic).

If you add lime to RO water you are adding alkalinity (which is the level of bicarbonates, carbonates, etc), of which Ca and Mg have the biggest affect. Thus it's best to simply call your water supplier (if you're on city/town water) and ask what for the level of alkalinity; if it's over 100 ppm then you can filter it through peat moss which will remove some bicarbonates and carbonates, thus lowering alkalinity.

Good luck with your test, it's nice to see ppl experimenting! However, what I wrote above is the best and most simple solution considering how much time it can take for RO filters to filter water, and then you are adding back what the RO filter removed? Kinda seem like ur chasing your tail (no offense intended).

desertsquirrel said:

From what i can tell the cutting edge cal amp that i use is only calcium chloride. Im about to do a side by side run with the ces amps and epsom/cal chloride. Let us know how yours works out.

Also I think carl carlson has a good tread on this subject.

Click to expand...

Calcium chloride is not a good choice, Ca nitrate is a better choice for a few reasons. CalMag+ offer Ca as Ca nitrate.

SupraSPL said:

The next experiment was to add some plain peat to the water and see if what the ppm would do. At first the peat lowered the ppm slightly and the ph of course. After a few minutes the ppm was up to ~30. After a few hours it was up to ~50 and the ph had risen back up to 7.2. Plain peat contains humic and fulvic acid so I assume these acids helped speed up the process.

Now I am wondering if there is actually any calmag available or if the acids locked it up somehow. If so, I wonder how much of that ppm is actually cal and mag ions. Any chemists have any input?

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Peat has humus, HA and very little FA. Peat has ions from the soil solution (from the bog) which will affect the TDS/EC. Peat is acidic, which is why it neutralizes some alkalinity from water, lowering ppm of water; however, the ions in peat will raise the ppm too.

FWIW, humic acid is not acidic (pH wise), it's basic. The use of the word "acid" is in reference to structure of HA, not it's pH. Most liquid HA is basic because once pH of liquid HA drops below about 3 the FA and HA will precipitate out of the solution. Most liquid HA products have pH over 8, I source a liquid HA product with pH of 5.5-6.

Thanks for the input spurr. You made a good point about chasing my tail I can see how it would look that way. I use the R/O water for brewing and also for drinking/cooking so I would have installed the R/O machine either way. Also, I need very little water (avg ~1 liter per day) so it is no trouble.

I agree 24 hour 100ppm tap water would get the job done but one of the main reasons I am trying to use R/O water instead is to avoid the extra compounds that can be present in tap water, especially mine since the source water is from a polluted river (pharmaceuticals, pesticides, herbicides, persistent organic pollutants, who knows what else etc) I also wonder about heavy metals. I looked at my local water report and it did not seem like they tested for all metals. For $140 I can play it safe with R/O seems like a wise investment considering the cost of health care.

Another reason I am interested in R/O water is because I would like to be able to control the level of mag during the flush to get the smoothest smoke possible.

I made an error in my post I meant to write humic acid and tannic acid. It is interesting what you said about humic acid being basic I definitely need to study up on that. One thing is for certain though, overall the peat is acidic and the lime has to work for hours to raise the PH up to ~7.2. I was surprised to note that the addition of peat did not immediately raise the ppm, it is surprisingly "clean".

I was hoping to avoid excess alkalinity from carbonates by going this route rather than spring or tap water, but it sounds like it is a byproduct of the reaction between carbonic acid and calcium magnesium carbonate? (Sorry if these are dumb questions but my understanding of most chemistry is weak.) For example I have a spring water source that is 175 ppm total. 100 or so is from bicarbonates, 32ppm is from calcium and 4ppm is from magnesium. The PH reads ~8.5 and it seems to have a somewhat strong buffer characterisitic. I was reluctant to use this water because I figured it would lead to a high soil ph after ahwile. I can't dilute it because the cal mag ppm seems low as it is. So I am trying to make my own version of sweet spring water without the excess alkalinity and hopefully an abundance of available cal mag.

The lime + peat + R/O sample rose from 4ppm to 72ppm in 3 days. The plain R/O water + lime also just hit 72 ppm but took 9 days.

I have a few jugs where the ph made it up to 7.6 instead of the normal 7.2. It may be because I added fresh R/O that had no time to absorb carbon dioxide. The jugs that are at 7.6 ph seem to be stuck at a given ppm for days. This shows that time is not really the major factor to dissolve the dolomite. So even 4 ppm water cannot do much, it is more a function of ph, it needs acids to dissolve the calcium magnesium carbonate molecule.

To test this I filled a PET bottle with only fresh R/O water that read 3.5ppm and 6.4 ph. I shook it for 15 seconds and the ph dropped right down to 5.7. I exhaled into the bottle and gave it another shake (15 seconds). The ph dropped to 5.0. One more and another shake (30 seconds) the ph dropped to 4.5. The ppm had risen from 4 to 7. I have no idea why the ppm rose, does that mean there is 3ppm of carbonic acid added?

I added this water to a jar filled with rinsed dolomite. It jumped to 8 ppm. I added plain peat and a squirt of wetting agent. The ppm read 12 and interestingly the fresh peat sucked a few ppm away. After a few shakes ppm began to rise quickly. The ph dropped to 6.3 but quickly rose to 7.2. The jar was up to 80ppm in only a few minutes. There is probably some optimum ratio of watereat:lime that would get the job done even more quickly so I will start looking for that.

The downside is that the 80ppm water looks dingy and has a few chunks of peat hanging around. Would be no use as a foliar spray and would be difficult to measure ph with liquid testers.

Apparently it works to just fill a jug with R/O leaving some airspace, add (rinsed) lime, exhale into the jug then shake it for 30 seconds. Exhale again and shake again. The ppm rose from 24 to 48 for me in just a few minutes and still rising fast. After stopping the process the ppm will continues to rise as carbonic acid interacts with the dolomite. The ph is still down at 6 my guess is the ppm will continue to rise until stabilizing at 7.2.

It could also be a cheap way to remineralize and raise the ph of R/O water for drinking. It would be nice to have a cleaner source of CO2, maybe exhale through a filter into an airstone or something.

I found a 40lb bag of pulverized dolomite lime at Lowes for $3. This stuff is basically powdered so the surface area is much greater than the pelletized lime even if crushed.

The first thing I noticed about the pulverized lime is that it does not need to be rinsed like the pelletized. The pelletized brought rinse water up to ~3000 ppm due to the coating but the pulverized only raised the 3ppm water up to about 12ppm in the first few seconds. It stabilized at about 25 ppm but when I added the carbonic acid it rose up to 80ppm in a few minutes, 130ppm after a few hours and 145 by the next day.

The downsides of pulverized lime are that it is dusty and it stays in suspension for ~12 hours. It refuses to move through a funnel so it needs to be in a container that can be scooped out rather than poured out. Other than those issues it seems to be getting the job done much better than pelletized.

Guaranteed analysis:
Ca 21.6%
Mg 10%
CaO 30.2%
MgO 16.7%
CaCO3 54%
MgCO3 35%

SupraSPL said:

Thanks I will look for the thread from CC.

So it looks like it takes almost 5 days for a decent amount of calmag to dissolve ~45ppm. I tried crushing the lime to increase surface area and that doesn't even seem to speed the process much. I also tried using a larger lime/water ratio and even that didn't seem to help.

The next experiment was to add some plain peat to the water and see if what the ppm would do. At first the peat lowered the ppm slightly and the ph of course. After a few minutes the ppm was up to ~30. After a few hours it was up to ~50 and the ph had risen back up to 7.2. Plain peat contains humic and fulvic acid so I assume these acids helped speed up the process. Now I am wondering if there is actually any calmag available or if the acids locked it up somehow. If so, I wonder how much of that ppm is actually cal and mag ions. Any chemists have any input?

Ehow has some info about pond water:

-Soften Water
Peat moss contains humic acid as well as tannic acid. Humic acid is a product of humus, partially or fully decayed organic vegetable or animal matter used by plants as a nutrient. When you add peat to hard water (water with high levels of minerals), the negatively charged humic acid molecules bind with both positively charged magnesium and calcium ions, removing these minerals from the water and thereby softening it.

-Lower pH
When molecules of humic acid bond with magnesium and calcium, the minerals release free positively charged hydrogen into the water, lowering the pH and thereby making the water acidic.

Click to expand...

wow you just answered why ive been having problems with my grow, looking like salt build up.

im growing in promix, so im guessing when i added humic acid it binded with my Ca and Mg locking them out leaving me unsure if it was a calémg def or nute burn.


than post helped me out alot as i couldnt figure out what the hell i was doing wrong

ps sorry if this is off topic