Growing with Hard Water

Botany and Cultivation
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@jgr The Ca in tap water is already available to plants. Any Ca in water that is dissolved in it will be present as Ca+2 ions, which plants can uptake. If you have water with high alkalinity, then that Ca+2 is present along with CO3-2 ions (carbonate anions). All of them randomly dispersed among the water molecules.

When you lower the pH, the acid reacts with the bases present (hydroxide ions and carbonate ions), but the acids do not react at all with the Ca2+. If the concentration of Ca+2 is not present at large concentrations (>300 ppm) then calcium sulfate will not precipitate, even if you added a molar equivalent to the Ca2+. For any precipitation to happen with phosphoric acid, there would need to be even more calcium present.

However, the conductivity of carbonate, sulfate and acid phosphate ions are all different, so the conductivity might change substantially. When you lower the pH you also turn carbonates into carbonic acid, which then turn into CO2, so that loss also causes a shift in conductivity.

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I’d gladly take you up on the nutrient profile formulation lol! Using RO in coco!

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Hi there, everyone!

I signed up, and arrived here, via a google search, because I am a novice cannabis grower trying (and struggling) with his native hard water source in St. Jacobs, ON, Canada!

Our water is currently testing from the tap around 310 PPM.

I got in touch with the region of Waterloo who provided me with this breakdown of their latest test results:

edit: had to delete the image

Yet I still am coming up with problems, especially in flower, with leaves either developing spots, or stems turning red, or so on.

Currently I was TRYING to make use of the native rich calcium and magnesium in the tap water to avoid having to dose with Cal-Mag, and use RO water. But it hasn’t been working yet.

Currently, for this run, I was attempting to simply use my tap water, dosed with absorbic acid according to this aquaponics spreadsheet: [Here is a water dechlorimination calculator spreadsheet for everyone. :edit: had to delete the link

To dissolve a lot of the chloramines and chlorines.

And then using pH Down to reach 6.5

Sadly, something is amiss.

Do these figures jump out as anything at a glance that could be made to work with?

Should I activate my RO system and cut it with the tap water? If so, to what PPM? My RO will come out around 10ppm tops so it’s in fine working condition.

I wish I could create a thread, but as a new user, I do not have access.

A huge thanks in advance for any input, and I’m happy to have found this forum

Thanks again

Cheers, from St. Jacobs!

edit - this is the most restrictive forum I’ve ever been on, it forced me to delete both my image and my link to the spreadsheet on reddit. Holy smokes.

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44

Can’t tell you much without knowing what’s in your water. Red stems in flower is usually indicative of a P deficiency. Are you mixing your own salts or using bottled/powdered nutrients?

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45

Just get an ro filter. The first place I grew had hard water, 250 ppm out the tap. The first crop had lots of yellow leaves and discoloration. I bought an ro, and it was an immediate difference. Subsequent crops had all green leaves.

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Ralf! I need your help man, how can I use my hard water supply coming out of the tap at 310-350 PPM? I have latest water breakdown from my region!

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Thank you all for the preliminary replies!

I do have my water report but the board won’t allow me to post them, that’s why I had to edit it out! I know the post makes no sense without it, I’m just not sure how to get it inserted here
Edit: Ahh! I can now post

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Neither, I am using KIS Mix Blended Soil | Black Swallow Living Soils, Brantford ON (blackswallowsoil.com) this product as a media, and trying to make use of my native hard water source… Without the need to introduce RO…

Sounding like growing with hard water really might be futile though from the preliminary replies :frowning:

I would also I guess be “content” with at least diluting the tap water down with RO, but to what PPM do I need to reduce?

The water comes out for me at 310-350 and the contents are in the table above, received directly from the lead engineer at Mannheim Water Treatment Plant in Waterloo

And my RO water is testing at 10-15 PPM from the dispenser. It is not DI, just RO

Thanks again

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49

I’d say your water is useable, especially since your in soil. I’d personally like to see chloride levels lower but there are those in the industry that think running CaCl is perfectly fine at much higher levels then you have.

I’d look elsewhere for the cause of your concerns.

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I would cut your tap with the RO. Down to 150 ppm.

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Puzzling then, the plants really just do not seem to like it after a while… The grow always starts OK especially in early veg but if I veg long enough the stems start turning red and leaves will show problems. And of course in flower as well… I’ve tried a multitude of things but just can’t seem to figure out what’s going on… It’s almost like something gets used up in the KIS Soil and when it does, it’s all downhill from this point… Usually why the small plants in huge pots end up going a much longer time before it happens…

Sigh

Thank you for your time and the reply

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Thank you, I was considering this as well. I was considering taking it all the way down to 50ppm even and then adding 100ppm or more (I was going to make a seperate post asking how much Cal-Mag in PPM to add to water) of this stuff:

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Since I already have it handy, I guess I bought it a while ago when I was first buying a bunch of stuff to start growing…

Grasping at straws trying to figure out how to keep these stems green

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I would stay away From the Ca/Mg for now. I I would think it’s safe to assume there is plenty of calcium and magnesium in your soil already. Adding more at at this time may cause issues. As I mentioned earlier red stems usually indicate a P deficiency. It’s possible the plants Are using up all the available P in the soil and need some supplementation.

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You can Bring your base water down to 50 PPM with your RO if you would like, but, I think you’ll be fine in the 100 to 150 range.

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Extremely possible - I am just a novice and don’t know much about it except what I’m trying to figure out through trial & error, or more importantly, asking on forums… Lets say I wanted to exepriment with adding more P into the equation - would this be something I should water in, or add as a dry amendment? I will go research this now as well

Thank you once again for your help!

Edit:

I just googled ‘p deficiency in cannabis’ - oh yes - this looks awfully familiar indeed

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You need to custom blend your nutrients from raw salts if you want to grow successfully with this. Phosphoric acid should be your only P source, reason why you shouldn’t be using normal nutrients. Normal nutrients will always cause you imbalances with this water composition. You should create your own one part solution, see my post here (https://scienceinhydroponics.com/2022/06/a-one-part-hydroponic-nutrient-formulation-for-very-hard-water.html).

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Thank you Daniel once again for the response. I have both downloaded the HydroBuddy app onto my PC, and have read over your post - but sadly am still a bit confused as to how to approach it. I am guessing I need to plug in some of the values from my water breakdown above which I will experiment with now… I have no doubt I can source the individual components from stores around here as needed, it’s just figuring out what to do. Not gonna lie, it would be pretty damn cool to say that I’m using a custom blend of nutrients too! It is really fascinating although seemingly way over my head so far