Pelletized Sulphur as a Solution to Alkaline Water?

[August]

Hey nuts,
I recently learned that our water supply here in Denver is treated to bring the water to a target pH of 8.8, with a low of 8.5 and a high of 9.2. From what I understand, this is much too alkaline for most plants to tolerate for long periods of time, and like any horticulturist, I'd prefer my plants to *thrive*.

I understand that one option is to get a pH test of some kind, and add acid (vinegar?) to my tap water, and test repeatedly until I get closer to a neutral or desirable pH. Which would be insane considering I would have to do this every time I fill up my watering can.

I work at a garden center and have spent a lot of time around products that are pelletized for use in pots and in-ground, that claim to lower the soil pH. Most of these are elemental sulfur pellets.

My question is, would using a product like that, say, in teabags (like fertilizer) be enough to counteract the high alkalinity of my water? I'd rather have something *in* the pots so that I'm not restricted to using a watering can and performing a science experiment three times a day.

If I'm just dumb wrong about how this chemistry actually works, feel free to enlighten me. For reference my most used soil mix is about 2:2:1 Napa 8822 / Perlite / sifted compost.

 

[Glaucus]

Why is the pH of the water so high? You should be able to call up a detailed report of your local tap water quality, that includes all parameters (30+). I assume that is a thing in the US as well.

Vinegar is poisonous to both microorganisms and plants. It is a weed killer and it is a preservative in food. Adding vinegar to water with a pH of 9.2 is not a good idea. You are just adding more potential pollutants to the water.
If your water pH isn't too high, say 8, and it is not buffered, you could potentially add vinegar to make it neutral without harm. But adding vinegar won't really lower the hardness of water too much. So even then it is a question of what you are actually achieving.

Seems best to RO the water, then add back reasonable amount of minerals so you aren't watering with near-distilled water.

Also, there seems to be quite a bit of misinfo out there regarding tap water, pH, chlorine, salts, health, plants, hardness, alkalinity, etc.

What do they do at the garden center?

 

[Tums]

Why is the pH of the water so high? You should be able to call up a detailed report of your local tap water quality, that includes all parameters (30+). I assume that is a thing in the US as well.

Vinegar is poisonous to both microorganisms and plants. It is a weed killer and it is a preservative in food. Adding vinegar to water with a pH of 9.2 is not a good idea. You are just adding more potential pollutants to the water.
If your water pH isn't too high, say 8, and it is not buffered, you could potentially add vinegar to make it neutral without harm. But adding vinegar won't really lower the hardness of water too much. So even then it is a question of what you are actually achieving.

Seems best to RO the water, then add back reasonable amount of minerals so you aren't watering with near-distilled water.

Also, there seems to be quite a bit of misinfo out there regarding tap water, pH, chlorine, salts, health, plants, hardness, alkalinity, etc.

What do they do at the garden center?

Yes, is the alkalinity of your water available in the water quality reports? This is separate from the pH in that it sort of measures how resistant/buffered the water pH is to change, or how much it will affect the pH of your media. If the water has high pH but low alkalinity, you may not need to take much action.

Anyway, I have not noticed any ill effects of adding vinegar to irrigation water. Plain old white vinegar is acetic acid which is actually a relatively weak acid. The stronger and more persistent "pH down" solutions used in hydroponics are usually phosphoric, nitric, or sulfuric acid. But all of those options are still manually changing the pH of your irrigation water. If you just wanted to add something to your pots and be done with it, I think certain types of fertilizer are "acid-forming" based on the type of nitrogen (ammonium, urea a little bit, and not nitrate) and can counteract low alkalinity water. As for sulfur, according to this link, it can take a long time to work because it's dependent on microbial action.

 

[Colorado]

What about a product like PH Down?

Citric Down - pH Adjuster

CITRIC DOWN will lower the pH level of your nutrient solution. The ideal pH for most hydroponic nutrient solutions is between 5.8 and 6.2, with some exceptions. Nutrient lockout will occur if pH levels are outside the optimal range. Citric acid is a weak acid and while typically it will drop pH...

futureharvest.com

 

[Glaucus]

Seems that pH down uses citric acid, also a weak acid (but stronger than acetic acid. Acetic acid being a weak acid is actually the downside. You need more of it to have an effect on the pH. Which means that a lot of acetic acid will not react with carbonate and will not neutralize it, which may be the aim. Regardless of pH, the concentration of carbonate will affect the soil pH and deacidify it.

Stronger acids will be much more effective at reacting with carbonate and turning it into CO2. You should not use sulphoric acid, hydrofluoric acid or hydrochloric acid, though. Nitric acid and phosphoric acid are better and will leave the 'fertilizer minerals' behind. However, you need to be really careful using it. Do something wrong, and you can kill stuff pretty fast and way harder than any of that hard water carbonate would have done.

Citrate and carbonate can both act as buffers in the pH 6 to 7 range.

 

[Bonsai Nut]

When I lived in California, I used a soil acidifier extensively on my trees - both bonsai and landscape. Water out of the tap was 8.2 pH-8.5 pH.

Based on the recommendation of commercial citrus growers in the area, I used this product. It included 10.5% sulfur as a soil acidifier:


A homogeneous fertilizer enriched with 11% iron & 10.5% sulfur. This is a complete, balanced, homogeneous, pelletized fertilizer. This special formula will help counteract alkaline soil and will enable plants to overcome iron-induced chlorosis. Super Iron® promotes good health, slower growth, and great color.

Interestingly, here in NC we have the opposite problem. People here regularly add lime to raise soil pH.

 

[August]

Why is the pH of the water so high? You should be able to call up a detailed report of your local tap water quality, that includes all parameters (30+). I assume that is a thing in the US as well.

In Denver we are still replacing many lead service lines, the pH is raised in order to decrease corrosion of said lines, and reduce the amount of lead in the tap water.

Vinegar is poisonous to both microorganisms and plants. It is a weed killer and it is a preservative in food. Adding vinegar to water with a pH of 9.2 is not a good idea. You are just adding more potential pollutants to the water.

As I said, I don't want to change the pH of my water at all if I can help it...

Seems best to RO the water, then add back reasonable amount of minerals so you aren't watering with near-distilled water.

While I appreciate this solution, I'm baffled that you suggested reverse osmosis, followed by mineral supplementation not only way beyond the scope of my ability but far more time consuming than just using pH down. Still I respect it

What do they do at the garden center?

Absolutely nothing! Garden centers are not nurseries; the scope of our plant care involves watering and pruning. Nothing more nothing less. At least, at my garden center

 

[August]

When I lived in California, I used a soil acidifier extensively on my trees - both bonsai and landscape. Water out of the tap was 8.2 pH-8.5 pH.

Based on the recommendation of commercial citrus growers in the area, I used this product. It included 10.5% sulfur as a soil acidifier:

View attachment 498856
A homogeneous fertilizer enriched with 11% iron & 10.5% sulfur. This is a complete, balanced, homogeneous, pelletized fertilizer. This special formula will help counteract alkaline soil and will enable plants to overcome iron-induced chlorosis. Super Iron® promotes good health, slower growth, and great color.

Interestingly, here in NC we have the opposite problem. People here regularly add lime to raise soil pH.

Great recommendation, this is reassuring. The products I'm looking at are fairly similar to this, in particular Iron-tone by espoma (17% sulfur, 6% iron) and their Soil Acidifier, which is 30% sulfur.

Did you find that the Super Iron product worked well to neutralize your hard water?

 

[Glaucus]

As I said, I don't want to change the pH of my water at all if I can help it...

So then just use it as is for your bonsai? Not saying your tap water is good or sustainable long term, but right now we don't know of anything in your tap water that is harmful.

While I appreciate this solution, I'm baffled that you suggested reverse osmosis, followed by mineral supplementation not only way beyond the scope of my ability but far more time consuming than just using pH down. Still I respect it

I think you have this a bit backwards. The pH that matters if the pH of your soil. The pH of the water doesn't matter too much. It just means there isn't a lot of H+ in your tap water.
If your soil has plenty of H+, there is no issue.

However, usually pHs are high because the water contains carbonate. And the carbonate that raises the pH a little bit can neutralize a lot of H+. Which means it has the ability to neutralize a lot of the acidity of the soil. Additionally, carbonate salts are not very soluble, so they don't wash out of your soil very easily once they deposit.
Additionally, pH 9 is quite high, so that makes me wonder about what they added to the water to raise the pH.

If you want to remove the 'bad things' that are in your tap water, you need to use something like reverse osmosis membrane. And then you need to add back the normal minerals, because plants need them. Otherwise, the roots will suffer osmotic stress because the soil is depleted in solutes. That is just how the (physical) chemistry works.

Absolutely nothing! Garden centers are not nurseries; the scope of our plant care involves watering and pruning. Nothing more nothing less. At least, at my garden center

And the plants don't die, right? So the pH 9 water isn't so bad after all? You just need to have acidic soil.

Another solution can be collecting rain water. But make sure you don't get a microorganism bloom in your collected rainwater that can also be harmful to the plants.

Iron sulphate is does reduce pH. But when people say 'iron' or 'sulphur', that can be a lot of different things.
Iron sulphate is an acidic salt. However, other forms may require bacterial activity to change/oxidize/reduce them.
Iron, Iron(II) ions, Iron(III) ions, sulfate, sulfide, sulfur, all different things.

 

[August]

@Bonsai Nut the thought also comes to mind that Osmocote contains about 6% sulfur, and I have some on hand. Do you think thats enough to actually make a positive change in the water / soil pH?

 

[August]

And the plants don't die, right? So the pH 9 water isn't so bad after all? You just need to have acidic soil.

Another solution can be collecting rain water. But make sure you don't get a microorganism bloom in your collected rainwater that can also be harmful to the plants.

Plants actually do die, and go chlorotic, quite often. Theres a lot of factors at play there; you have to understand most of the labor is highschoolers and retirees. Garden centers don't really have the manpower to individually care for every plant's needs... so I'm not necessarily saying it's a matter of water pH, but I definitely don't take "care" advice from there.

It's actually illegal to collect rainwater in my city :/

I think you have this a bit backwards. The pH that matters if the pH of your soil. The pH of the water doesn't matter too much. It just means there isn't a lot of H+ in your tap water.
If your soil has plenty of H+, there is no issue.

Additionally, pH 9 is quite high, so that makes me wonder about what they added to the water to raise the pH.

I'm more than a little unclear on this; chemistry is not one of my best subjects. Should I be testing the water that runs out of the pot to get an accurate perception of my soil pH? Are you saying that water with an alkaline pH should be no cause for worry? Not to bombard you with questions... but I am worried about the nutrient availability in my pots.

To answer your other question, the city adds sodium hydroxide to the water to raise its pH.

 

[Glaucus]

Plants actually do die, and go chlorotic, quite often. Theres a lot of factors at play there; you have to understand most of the labor is highschoolers and retirees. Garden centers don't really have the manpower to individually care for every plant's needs... so I'm not necessarily saying it's a matter of water pH, but I definitely don't take "care" advice from there.

Doesn't sound like good water then.

I'm more than a little unclear on this; chemistry is not one of my best subjects. Should I be testing the water that runs out of the pot to get an accurate perception of my soil pH?

Hmm, possibly. But not after you add tap water. You would test the pH of rainwater coming out of your pot. The tap won't really be changed by just flowing through the soil once.

Are you saying that water with an alkaline pH should be no cause for worry? Not to bombard you with questions... but I am worried about the nutrient availability in my pots.

Nutrients would definitely be way less available at a higher pH. But the soil has a buffering capacity. The tap water may or may not have a buffering capacity. Which is why alkalinity (not alkaline) is often discussed.
When you mix two solutions, one with a high pH and one with a low pH, you don't necessarily get an intermediate pH. It is not that simple, actually.

To answer your other question, the city adds sodium hydroxide to the water to raise its pH.

Ok this bit of info matters a lot. So your tap water pH is not that high because of boatload of calcium carbonate. But because of a tiny amount of strong base.
In that case, you can use something like citric acid (the pH Down product). The hydroxide is a strong base and will react with all the citric acid, heavily favouring the creation sodium citrate. Meaning they don't go to an equilibrium but to completion.
And because it is a strong base, there is only a tiny bit of sodium ions anyway. So that shouldn't be an issue.
And like mentioned before, sodium citrate acts like a buffer for a solution with a pH around 6. So that is also good. Because that makes it easier to reach that pH and stay stable around it.
Citric acid/citrate should be less toxic than acetic acid/acetate.

If you do this, then directly after watering, nutrient availability in your tap water will be much better than when you keep the pH at 9.
Otherwise, nutrient availability would only be good after it rained.

And if your pH had been high because of calcium carbonate, then every watering with tap water would slowly deacidify the soil.
Which would result in poor nutrient availability even after it rained.

9 is so high that it just makes sense to lower the pH no matter what. But I wanted to make the point that pH is just a number. And that it can reflect several different situations.
If your water had had 1000 ppm carbonate and you used vinegar to set the pH to 6, then that could have been a very toxic brew.

 

[Bonsai Nut]

Great recommendation, this is reassuring. The products I'm looking at are fairly similar to this, in particular Iron-tone by espoma (17% sulfur, 6% iron) and their Soil Acidifier, which is 30% sulfur.

Did you find that the Super Iron product worked well to neutralize your hard water?

I didn't do any testing other than to note the impact that it had on my trees - particularly citrus and azaleas, camellias and gardenias. They went from being weak and cholorotic, to dark green and healthy. It had a marked impact on pines and junipers as well.

 

[Glaucus]

Iron(II) sulfate don't neutralize hard water. It doesn't react very much with carbonate ions. You need a strong acid to neutralize carbonate and create CO2.
Iron(II) sulfate is a good salt to have in fertilizer for acid-loving plants. It indeed helps prevent or fix chlorosis while also acidifying the soil.

You should still check the alkaninity (not pH) of your tap water. What is the calcium carbonate and magnesium carbonate concentration?

 

[Tums]

Alright, I found the Denver municipal water alkalinity. If you expand "Water Quality Monitoring", it's actually quite reasonable at an average of 55.9ppm.

Treated Water Quality Summary

Need more details about your water? Your water’s journey starts as mountain snowpack and ends with the clean, great-tasting water that comes out of your tap. Last year, we collected more than 55,000 samples and conducted nearly 200,000 tests to ensure our water is as clean and safe as possible...

www.denverwater.org

In fact, they have a dedicated page on water hardness, which describes the water as "soft to moderately hard".

Water Hardness

Hardness in water is usually observed by its ability to form scale and softness, and is observed by its ability to make suds with soaps and detergents. If your water leaves deposits in sinks and tubs, then it is moderately hard to hard. If you get lots of suds with soap, then the water is soft...

www.denverwater.org

According to this UMass reference I like, Denver water easily falls within the acceptable (0-100ppm) alkalinity range.

Water Quality: pH and Alkalinity

Recently, some growers have expressed concern about the "high pH" of their irrigation water and its potential adverse effects on plants. The purpose of this article is to allay some of these concerns by pointing out the difference between "high pH" and "high alkalinity". Alkalinity and pH are...

ag.umass.edu

So if you use an acid-forming fertilizer, you should hopefully see good results without having to do anything else.

 

[Colorado]

Alright, I found the Denver municipal water alkalinity. If you expand "Water Quality Monitoring", it's actually quite reasonable at an average of 55.9ppm.

Treated Water Quality Summary

Need more details about your water? Your water’s journey starts as mountain snowpack and ends with the clean, great-tasting water that comes out of your tap. Last year, we collected more than 55,000 samples and conducted nearly 200,000 tests to ensure our water is as clean and safe as possible...

www.denverwater.org

In fact, they have a dedicated page on water hardness, which describes the water as "soft to moderately hard".

Water Hardness

Hardness in water is usually observed by its ability to form scale and softness, and is observed by its ability to make suds with soaps and detergents. If your water leaves deposits in sinks and tubs, then it is moderately hard to hard. If you get lots of suds with soap, then the water is soft...

www.denverwater.org

According to this UMass reference I like, Denver water easily falls within the acceptable (0-100ppm) alkalinity range.

Water Quality: pH and Alkalinity

Recently, some growers have expressed concern about the "high pH" of their irrigation water and its potential adverse effects on plants. The purpose of this article is to allay some of these concerns by pointing out the difference between "high pH" and "high alkalinity". Alkalinity and pH are...

ag.umass.edu

So if you use an acid-forming fertilizer, you should hopefully see good results without having to do anything else.

Thank you very much for posting this - very helpful. Given that the ppm appears to be acceptable, but the ph is still very high, I am wondering what your and @Glaucus recommended remedy would be. Would an RO system help with this?

 

[August]

Thanks @Tums ! I've been working all day and trying to respond / find the appropriate resources when I can. What would you consider as an "acid-forming" fertilizer?

Im glad to hear that alkalinity might not be as scary as I supposed. We have very alkaline soil in the ground here; leads to lots of issues with nutrient lockout in planted trees, red maples etc. So it has been on my mind. Especially with the tap water issue.

 

[Tums]

An RO system will ensure your water has low alkalinity, but then you'll have to have to ensure that your plants are getting enough calcium/magnesium and you'll have to figure out what to do with all the wastewater. I'd personally rather just add acid to tap water.

Acid-forming fertilizers will have more nitrogen as ammonium (most acidifying)/urea (somewhat acidifying) instead of nitrate.

 

[nuttiest]

August and Bnut are right to think about usefulness of sulfur, but it takes a long time and the right bacterial biome.
The best way to buffer in the garden is gypsum, or calcium and sulfur. Not so popular anymore, but people used plasterboard and plaster even.
SulfATES are useful right away in between fertilizing if you don't fertilize often - aluminum sulfate, magnesium sulfate, and good for in fall is potassium sulfate. But complete fertilizers usually have one or two already.
The important thing is like said by Glaucus soil can usually buffer this high ph just fine - but you know how things start looking when no rain for a long time and only tap water... Like white crust on soil and trunks? I think at that point it is time to intervene with fertilizer or chemicals just to help soil ph.

 

[nuttiest]

Don't forget about in line hose filter if you don't want to screw around with watering cans or teabags. I think i talked myself into it after reading this thread.
Anyone have reviews for a filter?