My attempts at adjusting pH (for plants) with vinegar and citric acid

We use well water here, which is a little on the hard side. Tomatoes tolerate it, but most other plants start to struggle once past the seedling stage – I would guess it’s because any buffering capacity in the soil has been overcome and the soil is starting to resemble the pH of the water that’s been used.

In the past, I’ve used a few tablespoons of vinegar when watering blueberries that had started to brown, and more recently when I’ve been too lazy to distill water (it takes so long!), I have used 1-2 tablespoons of vinegar in a 4L watering can for spruce (a random guess that has kept them alive thus far).

Fast forward to today, and I figured it was about time to start getting correct pH levels!

Before I get to the numbers (what amounts of citric or vinegar resulted in what pH levels), I’ll mention how I arrived at them.

I grabbed a digital pH meter from Amazon. This is the common cheap yellow one sold under such highly renowned brands as “Dr. Meter”, “Etekcity”, “Dr. Health”, and “Xcellent Global”. They all look pretty much identical, all have mixed reviews, and the biggest difference seems to be how many packets of calibration/buffering powder they come with (if any). This is what it looks like:

pH meter used for testing2 of the pH buffer packets that came with the meter

Calibration and why accuracy went out the window quickly

There’s a 6.86 and 4.01 pH packet that you’re supposed to use to calibrate. Add the 6.86 to 250mL (a cup) of water, mix it up, stick the meter in a little and adjust the screw. Then do the same with the 4.01 pH packet with a new cup of water.

I did this with distilled water and had the same issue that others have run into: You could calibrate it at 6.86, but then it was a little off at 4.01 (showed 4.10). Calibrate at 4.01 and it’s off at 6.86 (showed 6.65).

Since plants usually tolerate wide pH ranges like 5.5-7.0, this wasn’t a huge deal for me. As long as I’m not at the min/max, it’s not the end of the world if I’m off by 0.1 or 0.2.

The Numbers!

  • pH of the tap water: 7.5 – 7.7 pH
  • pH of water run through the distiller: 6.1 – 6.3 pH

The distilled water’s just listed for reference. It’s expected to be a little acidic since it absorbs CO2 and forms carbonic acid, getting close to 6 was lower than I had expected. I measured a few times (and a few samples) to be sure.

3.5 – 4L of Tap Water (7.5 – 7.7 pH) with Citric Acid added:

  • 1/8 tsp citric acid: 6.1 – 6.3 pH
  • 1/4 tsp citric acid: 5.3 – 5.5 pH
  • 1/2 tsp citric acid: 4.4 – 4.6 pH
  • 1 tsp citric acid: ~3.5 pH
  • 1 tbsp citric acid: ~2.5 pH

Note that the watering can was filled with tap water to roughly 3.75 L and thoroughly rinsed after each attempt. Measuring out powder is easy too, so I’m fairly happy with these numbers.

Because such small amounts of citric acid have such a large effect, I wouldn’t recommend using citric acid to adjust your pH if operating in “guess mode”. You really need to measure stuff here (and know your original pH) since it doesn’t take much to get into plant-killing territory.

Even with a pH meter, an accidental double-dose or poor measurement could have a drastic effect, so keep that in mind.

3.5 – 4L of Tap Water (7.5 – 7.7 pH) with Vinegar (5% acetic acid) added:

  • 1 tbsp vinegar: 5.8 – 6.0 pH
  • 2 tbsp vinegar: 5.4 – 5.6 pH
  • 3 tbsp vinegar: 5.0 – 5.2 pH
  • 4 tbsp vinegar: 4.5 – 4.7 pH
  • 5 tbsp vinegar: 4.4 – 4.6 pH
  • 6 tbsp vinegar: 4.2 – 4.4 pH
  • 7 tbsp vinegar: 4.1 – 4.3 pH
  • 8 tbsp vinegar: 4.0 – 4.2 pH
  • 9 tbsp vinegar: 4.0 – 4.2 pH (actually 0.07 less)

I was pretty sloppy measuring here since it’s a little cumbersome to pour from the jug of vinegar into a little tablespoon. The difference between 8 and 9 tbsp was really small (0.07), which is why I stopped there. Getting below a pH of 4 wasn’t going to happen without a *lot* of vinegar, and we’re much too acidic for most plants at that point anyway.

The really interesting thing to note here is that things REALLY started to slow down once I hit a pH of about 4.5. I’ve read about spruce being fine at 4.5 and tolerating as low as 4.0. That gives a lot more leeway than I had expected – spruce might be a little tough to over-acidify with vinegar (within reason).

If nothing else, “ballparking” pH with vinegar should be a lot safer than trying to ballpark with a stronger acid, particularly when dealing with more acid-loving plants (spruce/blueberries/etc). I had previously been using 2 tbsp – turns out, they probably would have survived anything up to 9.

Citric Acid and White Vinegar (5% acetic) that were used

Anyway, I’ll leave it at that. This is mainly for my own use, but if you’re reading around and trying to “guestimate” how much you’ll need to acidify your water, hopefully you find something above to be helpful.

However, keep in mind that my tap water is undoubtedly much different from yours. Different starting pH, different dissolved minerals, etc. What brings my water to a plant-happy-place might turn your water into a plant-death-solution, so try to get a hold of some pH testing materials. If that’s out of the question, at least search around to see what results others have come up with ;)

 

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  1. Saroj on March 8, 2016 - click here to reply
    Thanks for this... it also informed me that I could use an inexpensive pH meter to test my well water which is acidic. I have a neutralizer (uses calcium to raise it). I really appreciated your analysis of the CREE vs. VERO cobs as well... quite helpful.
    • aussiejack on November 23, 2016 - click here to reply
      Hi. I was just browsing to see if vinegar would quick-fix a pH of about 8.5-9.0 in a small tomato patch.The tom plants are smaller than they should be,but otherwise healthy.Ditto 3 corn plants in the same patch,siblings of 18 others elsewhere in the garden that areabout 4x bigger.I've got a chemistry background..your "experiment" was elegant and informative.I'll apply the vinegar as soon as I log out here. Thanks mate.(I'm in Sydney,Australia)
    • Sam on March 31, 2018 - click here to reply
      You may not need to neutralize your water, a lot of plants like more acidic environments. It's definitely a pain where I live, since the water has a higher pH, and I had to lower it's pH after realizing it was making some of my plants not grow as well.
  2. Trista on June 22, 2016 - click here to reply
    OHMYGOSH thank you so much for this science experiment! I've been scouring the internet for something like this lol. I've read everything from "a cup of vinegar" to "half a teaspoon" per gallon of water but no one had evidence to back up their (apparent) guesses! Now I can give my blueberries a quick boost when the well water is wreaking havoc on the pH and I can't get to the store for some sulfur. Thanks again!!
  3. Dunny Junyon on February 6, 2017 - click here to reply
    Ooops...I should have read this first. Over vinegared my hibiscus and the leaves fell off.
  4. aiteeman on July 17, 2017 - click here to reply
    Hi. Thanks for the info. Should have read your article before conducting my own "experiment". Got almost identical result as yours.
  5. Anonymous on August 17, 2017 - click here to reply
    Thank you! The data on reducing tap water pH using vinegar was exactly what I needed, and I found it instantly. Now I'm sort of at a loss since I expected this to take at least an hour...
  6. Paul UK on October 9, 2017 - click here to reply
    Great info, many thanks. Saves me doing the same experiment to keep my blueberries happy :)
    • Anonymous on July 2, 2018 - click here to reply
      Much thanks for your time and trouble on this issue. Internet recommendations are all over the place. You are methodical scientific approach is just what the doctor ordered! Cheers, Albert
  7. James on November 13, 2017 - click here to reply
    As a newbie, I am learning a few things about pH. You guys are good.
  8. Rev Dr Travis A Foster I, Esq. on December 21, 2017 - click here to reply
    The point he made at the end about everyone’s water being different is very important. Last night I used this as a guideline to lower the ph in my hydroponic system. My reservoir is 12 gallons and was sitting at ~7ph and was aiming for around 5.5. I figured I needed around 20T to get there. I used 18T then checked. My ph solution only works down to 4 and would be an orange color, the solution turned bright red! This is a ph so low there isn’t an indicator for it. I went ahead and used some ph up to correct and it took a ridiculous amount just to bring it up into range. My fault not his. I should have added the vinegar slower and checked along the way. The grow bed has six tomato plants about 6 inches a piece and four pepper plants from 2 to 6 inches all freshly transplanted that day. So far I see no ill effects in the plants but definitely had me worried for a bit!
    • Boogy on September 30, 2020 - click here to reply
      Having high ph problems in my hydroponic reservoir too. It takes 3 five gallon buckets to fill mine and the tap water always reads 7.5 so I add vinegar to each bucket of water till I get the ph down to 6 then pour it in my resevior. A day or 2 later I check the ph and it's back up to 7.5 so I add vinegar and stir till its back down to 6 and next day or 2 it's back up to 7.5 again.
      • Anonymous on October 14, 2020 - click here to reply
        Not sure if this will help you but it may be the calcium content in your water that keeps bring your pH back up. From my understanding you'd have to keep adding pH lowering substance until the buffering abilities of the calcium is neutralised or removing the calcium from the water in order for the pH to stay at the level your after. If you can remove that calcium and then try adjusting the pH to see if it remains lower. I don't know much about hydroponics, my experience comes from aquaponics, if the water in your system recirculates other factors like if the grow media has stone that has lime in it then it'll keep buffering your water back up and apparently plants in different stages can change the characteristics of the water by the waste the roots release. I found some of this info on the canna website, the article was about EC and pH in hydroponics with their products etc. https://www.canna.com.au/everything_about_ec_and_ph_using_aqua
        I've also been using vitamin c to remove chlorine from the water.
        Hope this is helpful.
  9. Ed on March 1, 2018 - click here to reply
    Thanks, really helpful info. Will be potting up some blueberries soon and no easy access to rainwater so if needs be can have ago At acidifying some tap water, should I run out of rain water. Nice one :)
  10. Encourager on March 18, 2018 - click here to reply
    Thanks for the article. I completely forgot our hard well water!!! We have set up rain barrels and will use them exclusively for our raised bed that we have been having so much trouble with. I added way too much manure two years in a row, to the point where moss was growing and water sat on the top. My bad. My pH is over 8, probably closer to 9. N is depleted as is the phosphorus with potassium not even registering on the chart - way too high. Sigh. I bought 20% organic vinegar to kill nut sedge which was in some organic mulch we bought. So have lots on hand. Would that be sufficient to lower the pH???
    • 20% is higher than the common 5% acetic acid that I used, so at the very least you'd have to significantly reduce the amount you use. It's a situation where a PH tester is ideal. If you can't get a hold of a PH tester and are left to guestimating, I'd be inclined to try a mix/solution on a smaller area for a while first to ensure the concentration isn't going to harm your plants.

      If it's a large raised bed that requires a lot of watering, it could be worth looking into sulfur bags (often found as "garden sulfur"), since they break down over time and acidify the soil. Getting the concentration right can be tricky, but if you start with smaller amounts and test the soil PH every couple months you should be able to get to a point where you know roughly how much to add annually to keep the soil at the desired PH.
      • Encourager on March 18, 2018 - click here to reply
        Thanks Matt. Actually the bed is empty right now, waiting for pea planting...at least it was until I did the soil testing.
      • Suja on May 27, 2020 - click here to reply
        Hi Matt,

        Thank you for this article. I’m trying to grow blueberries with the soil and water ph levels neutral. 4tbsp of vinegar in 4l of water will work I think. How often should you use (Daily or weekly) and how much per plant - 4litres? I don’t want to overdo it. Thanks. Suja.
        • In pots with well-drained soil, I was doing it every couple of days. Outside I've trended towards using sulfur as a longer term solution. If the leaves are green and it's growing normally, I'd just water as needed.
  11. Anonymous on May 18, 2018 - click here to reply
    Hi there. Is PH test paper reliable enough to check tap water PH?
    Thank you,
    Calling from Europe ☺
  12. Mr. S on June 29, 2018 - click here to reply
    Great stuff. Thanks!
  13. Robert Rowe on July 7, 2018 - click here to reply
    I purchased a 44 gallon garbage can for my rainwater collection. It is softer and its PH is usually 7 which my garden tolerates. When it does not rain for a week I will fill the can with my tap water 7.4 PH. Through research I have found that 2 cups of clear vinegar will reduce my water PH to 6 PH which is optimal for all of my garden plants. Citric acid uses a lot less for my 44 gallons but is hard to find in stores. Vinegar is cheaper and my garden thrives
  14. Anonymous on July 9, 2018 - click here to reply
    Wow ! Nice pH's Here we can have rainwater with pH 8.5; the tap water is pH 8+ ; The aquaponics bed, ~5yrs old, has pH close to 7.4 this must be because of the organic debris....Now we want to add almond leaves to the fish tank...meanwhile, all the plants which we water with the pond water are turning from yellow-light green to a Dark Rich green Baruch hashem! that made such things to be!
  15. nzme on October 31, 2018 - click here to reply
    uk tblspn or american net tells me us is 7 . something mls and uk and here in nz its 15 mls bit of a difference
    • Matt Gadient on October 31, 2018 - click here to reply
      Really good question. I hadn't realized this was one of the measurements that varies by region. Google's converter shows US/Imperial of 4.9ml/5.9ml teaspoon and 14.8ml/17.8ml tablespoon. Wikipedia currently suggests 5ml teaspoon for both, 14.8ml US tablespoon, 15ml UK/Canada tablespoon, and 20mL Australian tablespoon.

      I just measured the capacity of all our measuring spoon sets (these are typical sets used for cooking). Surprisingly they all varied. They're older sets, but I really get the impression the manufacturers didn't care much for accuracy. Then again, looking at the differences between Wikipedia and the Google converter... I have to wonder if there's any consensus on what the capacity should be to begin with...

      In any case, 5ml teaspoon and 14ml tablespoon is what I came up with in measuring the capacity of the spoons I used.

      Assuming your New Zealand tablespoon is actually 15ml I suspect you should be alright. Obviously a pH meter or some test strips are ideal though.
  16. DesertMann on December 28, 2018 - click here to reply
    thansk a lot, great article, though I am reading it to lower my hair rinse water. please see if I did it right... my starting bottle water is 6 ph I wanted 4.5 ph .... i need to do one cup which is one forth of gallon... so to do that I realize it would be half a tea spoon of acv vinagre... am I correcto? hair ph is 4.5 for your info.. after showering it is good to rinse it with 4.5 ph water... it is good for hair, dandruff , and lower hair loss.. etc.. so am I right in calculating ... I dudce that from your calculation... and having in mind that table spoon 15 ml is 3 time tea spoon which is 5ml. so could you test it on botttle water.. or tell me if i did right... thanks.
    • DesertMann on December 28, 2018 - click here to reply
      sorry one cup is one forth of litre... not gallon
  17. Anonymous on January 3, 2019 - click here to reply
    Thank you very much. I have been looking for this info to help my tap water. It is at pH level 7.4.
  18. Omar on March 1, 2019 - click here to reply
    Matt, one thing about your experiment that you're not taking into consideration and that might make the pH numbers not significant for other people is a measurement of alkalinity or how much dissolved carbonate equivalent minerals are in your water for example magnesium and calcium. You could have a pH of 7.8 and have high alkalinity and you could be dumping tablespoon after tablespoon of an acid and the pH would lower very slowly or you can have a pH of 7.8 with very low alkalinity and only two teaspoons of an acid and it'll drop immediately down to four, so alkalinity definitily needs to be considered when you're asking yourself how much acid to add, and for sure it's a good thing to measure the pH directly to know hows changing. I figured I would throw that in there so you have more of a perspective on the nuances of pH applications.
    • Sure. So the last paragraph did already mention the possibility of different dissolved minerals. Your description of the impact of that may certainly help anyone who's curious as to why that matters though. Thanks!
  19. Anonymous on March 16, 2019 - click here to reply
    Great write up!
  20. Anonymous on May 3, 2019 - click here to reply
    how long will vineger keep the ph lower
    • There isn't a simple answer here, and you'd need to test the soil pH to get an idea as to the short and long term effects.

      That said, if your soil is alkaline, I suspect you'd want to continue using the pH-adjusted-with-vinegar-water until other longer-term soil acidifying amendments (garden sulfer etc) have taken effect. On the other hand, if the soil is sufficiently acidic but your water is extremely hard, you may need to adjust the pH of the vinegar continually until you get access to rainwater or distilled water.
  21. Ian on May 17, 2019 - click here to reply
    Nice one...?
  22. Art on November 11, 2019 - click here to reply
    If no meter, there is always litmus paper too
  23. Carmine on November 24, 2019 - click here to reply
    Citric acid is usually available at wine and beer making supply stores many have on line purchasing capability. Try "Beverage People" in Santa Rosa, CA
  24. Anonymous on December 5, 2019 - click here to reply
    I have same ph tester and it says you.need to use all three only if you want to measure .01 but if you just want .1 then you only need to use one pack its a little confusing the way they word but just double check my g!
  25. Mohsen on December 19, 2019 - click here to reply
    Hi
    I lower water ph using citric acid to 6 but after couple of hours the ph raise to 7 again. Whats the reason for this?
  26. Behnam on January 15, 2020 - click here to reply
    thanks a lot for the info. very useful one.
  27. Joe on January 29, 2020 - click here to reply
    Hi,

    I’ve managed to adjust the pH of the water to 5.5 but it jumps back to 7.2 the day after. Is there any reason for this?
  28. Andy Hill on February 9, 2020 - click here to reply
    Hey Matt, Thanks for the great article. I make pickled eggs and have been in the process of switching from 50/50 white vinegar and water to using citric acid. I did buy a tester like you show in your pictures and it works great. I got just about the same results you did. Some people said they didn't like The vinegar flavor, so I thought what could be an alternative and I have used. Lemon juice and lime juice, which works great. But what's funny is if you do use citric acid in water and taste it it just about taste like vinegar anyways. I agree with you that the manufacturers go a little overboard on the accuracy of the machine. If you're in a laboratory and someone's life is in the balance go buy some big huge expensive thing. But for doing it for home use it works great. Thanks
  29. Nobody Important on February 12, 2020 - click here to reply
    pH is a logarithmic scale. It is the logarithm of the concentration of [OH-] ions. That means ph of 6 is one half of ions of ph7. 5 is one half of 6, and so on. Changes are rapid around 7ph and way, way slower at 2 or 12.
  30. Anonymous on February 14, 2020 - click here to reply
    Kids project question.
    Initial ph of soil was 7.6. Organic matter 4.1
    After watering soil with 5 different fluids that had corn growing in it for 5 weeks, the soil pH all went up
    Soil watered with
    DI Water. Resulted pH 8.2.
    Vinegar mixture. 8.9
    Tap water 8.3
    Apple juice 8.5
    Milk 8.4

    What is the chemical reaction that would cause the pH to go up? Especially with the Vinegar solution ( pH of 2.6)
  31. Jesse on April 15, 2020 - click here to reply
    Thanks so much for your posting this...... it was exactly what i needed, i have high ph water and crops don't do well at all....this helps. I was wondering why my blueberry plant was so scrawny and dead looking!
  32. Bob. on April 18, 2020 - click here to reply
    Really interesting article and experiment Matt.

    Just a quick question

    If all were equal and your water was a pH of 8 would the same amounts of vinegar drop the ph the same amounts.
    i.e 1 tbsp would drop the ph to 6.1-6.3.

    Is that correct or do the equations change a lot depending on the starting pH?
    • Hey Bob. All else being equal, at a higher starting pH it should take less acid to drop the pH by X "points". So as an example with random numbers, if it took 5mL of a certain acid to drop the pH from 9.0 to 8.0, it might take 8mL of that acid to drop pH from 8.0 to 7.0, and 32mL of that acid to drop pH from 7.0 to 6.0.

      To some degree you can see that behavior reflected in my results. The first smaller "hit" of acid in both cases dropped pH substantially compared to further tests with larger amounts. If my water had started at a pH of 10 I wouldn't be surprised if the first tablespoon of vinegar brought the pH down to under 7.
      • Anonymous on April 20, 2020 - click here to reply
        Thank you very much for the quick answer Matt, much appreciated and very helpful .
  33. Anonymous on June 8, 2020 - click here to reply
    Thank you for sharing your wisdom. I will be trying this tomorrow.
  34. Sharon B on June 18, 2020 - click here to reply
    Thank you so much for this. I am new to gardening and am starting with pepper plants and basic herbs and greens. I am using pots for everything so I am trying to be particularly attentive to the soil conditions. This is much better than my pout and pray method. Thank you for your time and scientific approach
  35. Anonymous on July 1, 2020 - click here to reply
    Cool. Great info. Thanks so much.

    Pete
  36. Anonymous on September 14, 2020 - click here to reply
    Hi,

    Do you need to use this for watering all the time instead of tap water or just every few months? I have skimmias in pots and the ground that get a bit yellow? Have been nurturing with erricaceus compost and acid plant feed but religiously watering with hard tap water.
    Thanks
  37. slowpoke on September 25, 2020 - click here to reply
    My water company's quality report tells me my tap water ph varies between 7.6 and 7.9 so this little experiment should be quite useful, thank you!
  38. Dave on December 22, 2020 - click here to reply
    Thanks for your work and illustrations of the issues.
  39. Gerald on April 20, 2021 - click here to reply
    I tried to duplicate your experiment but there were contradictions between your measurements and mine..
    My pH meter is accurate to .1 for the digital readout of pH. I used vinegar at 5%.
    1. I measured 4.12 pH for 3.5L with 4.33 tbsp. You measured 4.1 pH with your tbsp of 7. 7/4.33 = 1.6
    2. I measured 4.2 pH for 4L with 1.667 tbsp. You measured 4.2 pH with your tbsp of 8. 8/1.667 = 4.8. If I average these two ratios I get 3.2 which is close to the ratio of tsp to tbsp.The initial equation is pH = C1 * tsp^C2 where the values for C1 and C2 are given below for water amounts of 3.5L, 4L and 5L.
    The power fit to the data is very close between the equations and the data.
    *** Are you sure you used tablespoons and not teaspoons? It would be helpful if someone else checked the author's tests results and the my results. *** The difference is significant..
    My fit to the data for 5L gives me the equation pH = C1 * x^(C2) for 5L where x = tsp; C1 =7.99, C2 = -0.239
    For water amounts C1 C2 pH
    Summary: 3.5L5.46 -0.157 pH = C1 * tsp^2.
    for 7.75 pH water4L6.38 -0.179 pH = C1 * tsp^2
    5L7.99 -0.239 pH = C1 * tsp^2 where pH = 5 pH for 7.1 tsp for 5L of water with starting water pH of 7.75
    • Gerald on April 25, 2021 - click here to reply
      I checked my equation for 5L. New C1 = 7.05 and C2 = -.192 instead of 7.99 and -.239 above. I also found that it is a mistake to add 5% vinegar by Tablespoon rather than by weight. As I reviewed my data, it became clear that it was too hard to make accurate measurements by tablespoon by doing an experiment on myself by recording the weight of each tablespoon that I added. I was always short and often off by an unacceptable error. Each tablespoon should be 45 grams when added. Doing this by weight is superior. I could do the equations again but will not do so immediately. Just thought I would give everyone a heads up until I can redo the mixtures and also do a more accurate curve fittings so that a user can specify the amount of water, pH and the equation will give you, the grams of vinegar needed to add to the mixture will be right and accurate. A user just has do his/her own experiment to verify that it is worthwhile to do a quality experiment as described and then mix future combinations to obtain a very good pH accurate result without needing to overuse the accurate pH meters since they have a lifetime of somewhere between 1 month and one year depending on use.

      Lesson learned: Do all water measurements by weight using an accurate scale and add the vinegar also by weight using an accurate scale. Also use a pH meter that is accurate to .01 to construct table for amount of water that you want to mix with vinegar. Once that is done, you will not have to use your pH meter if you weigh the water and the vinegar.
  40. Eko on June 15, 2021 - click here to reply
    what dimensions are you talking about?
    teaspoon : 5 ml
    tablespoon : 15 ml

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