Lowering pH of well water for citrus - not with vinegar?

I just read Drew’s comment on a question re: peaches. A lightbulb went off in my head! Maybe my pH lowering efforts have been counterproductive.For watering my greenhouse citrus I’ve been adding vinegar to my well water- pH7.3 to lower it to 6.5. I have an accurate meter that reads pH. So I should be using sulfuric acid instead of vinegar in order not to release Ca+?

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Expensive Chinese probes don’t work either.

I use a Hach kit in the field (cheap, drops of indicator) and a Hach probe (900+, expensive, probe needs replaced often because we abuse it with mine water) when it’s warm out. The digital probes do not like the cold.

I guess “cheap” is relative… These are still expensive and I bet for fruit growing purposes that more affordable knock offs exist. For what it’s worth, the color wheel like this one pictures is harder to read. We have one that has a wheel that has a continuous color change pattern (like a rainbow with shades) also made by Hach that I find significantly easier to use. I’m not sure if it’s a different model number or just an old model.


If you drink the well water be careful with lowering it. Low water ph can cause bad health problems.

I grow a few Citrus in pots,but not long enough to really know what is an optimum pH and some other things about them.
But,when visiting the SF Bay area and walking through neighborhoods,with Lemon and Orange trees,loaded with fruit,it makes me wonder,if their owners do any tweaking to make the soil better for them.Also,it’s fairly well known that a lot of California’s soil is alkaline.Maybe that part of their requirements,is not too crucial.

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Using vinegar isn’t going to release calcium. Vinegar is just dilute acetic acid and it doesn’t contain calcium. The small pH adjustment you’re making with your well water shouldn’t cause issues with leaching calcium from your soil. Many people use water with a pH of 6.5 or less. Rainwater actually has a much lower pH since it absorbs carbon dioxide from the air. Typically rainwater has a pH of about 5.

You could continue to use vinegar. Or you could use citric acid which is a weak acid (like vinegar) and is available in powder form. You can find it at the store with canning supplies since it used for canning.

I would avoid using sulfuric acid because it is a strong acid and can cause chemical burns. If you use sulfuric acid please read the SDS (safety data sheet) and use appropriate PPE- gloves, goggles, PVC apron, etc. for the volume of acid you are using.


I say use what works for you. We do have a lot of new people on this forum, and old posts get buried. So it’s good to go over what we have discovered through the years on this forum. So it’s cool to go over what we use for pH or whatever the subject is.
I use MColorpHast™ Premium pH Strips
I use the 4-7 detection range. As I don’t need to know how basic something is, I just need to know lower range, anything over 6 is no good.
These are used in industry and are super easy to read. Meant for liquids but if you bury in soil and water with distilled water, you can get a very accurate reading of the soil.

So here is some tests I did to show how these look.
I dipped the strip in pure rainwater. Looks about 4.5 or 4.6.

OK here is my tape water, well I don’t know what the pH is? Just that it is over 7!

I had a couple blueberries die on me, and when I tested the pH it was under 4.0. It was too low and I killed them. So you do need to check once or twice a year to see where you are at. Especially if you use sulfur or sulfuric acid to lower pH. It’s hard to kill blueberries with a low pH, citrus would be much easier to kill! So be careful and conservative with acids, You can easily overdo it with these products, and it’s long lasting. Drench with tap water a long time to remove the acid. This is usually not an issue with vinegar and citric acid as bacteria remove these acids in about a month. Then the carbonate is released again.
You can flush out carbonates in containers by continuing to water once the acidic water runs out the holes. If you do this monitor pH as it could get too low. In containers it’s not a bad idea to drench containers to remove salts if using non organic fertilizers. They can build up. Here it rains enough they are often drenched!
I always liked what Fred Hoffman (Farmer Fred) said one day. “The more plants you kill, the better gardener you are” I must be an expert! :slight_smile:

And the water also is very basic! Don Shorr a nurseryman in Davis Ca has mentioned on his radio show the local ph. It depends on water supply as it changes when in drought in Davis at least. Both sources are in the 8 plus range.

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Drew 51:
My pH meter works great (Aptera 20). Could you elaborate some more on your issue with using vinegar to lower pH of well water? This is for ghouse citrus where the only water applied is well water pH 7.3 With a tsp of vinegar/2 g water I can lower water’s pH to 6.5. Are you saying this effect will be reversed or nullified within short time and cause a release of Ca+? Have you tried your other methods to lower pH? My rainwater’s pH is 7.2 so only a slight improvement over well water.

Christine, are you confident in your pH probe accuracy? Rainwater across the country should be providing a value no higher than 6.2 from what I can tell from this map.

Have you recently calibrated your probe with fresh solution? I know our calibration solution goes bad every few years and needs to be replaced. Also a probe should be calibrated just about every time you use it and it should also be kept moist between uses (and soaked in water for a good amount of time if it becomes dry). I’m not saying for sure your numbers are incorrect, just trying to help troubleshoot because I play this game at work all the time.

Yes I calibrate in pH 4 and pH 7 stock solution each time. The probe is kept moist.
After trying many other meters, I am totally confident that this Aptera meter is accurate. Readout is digital, not color wheel, which is easier to use. I saw that the thread got kinda off track talking about meters - we love to love, or trash, our devices!
My question is whether vinegar added to well water is effective to use with citrus to lower pH. I can lower pH7.3 well water to 6.5 by adding 2 tsp vinegar to 2 gallons water. However, I’ve noticed that if I let pH 6.5 water stand in watering can for a few days, the pH rises back to original pH7.3. So maybe vinegar forms carbonic acid and is released to air.

I’ve seen a similar phenomena when I raised fish in an indoor aquarium. My Ph7.3 water would gradually creep upwards (to 8.3) the longer it flowed through the system. I solved this by bubbling CO2 through the water to maintain optimal pH - expensive and not something I plan to do now.
I could never understand when and where I would ever use the (long-forgotten) facts from chemistry class - and here I am!

I just took the pH of seltzer water produced by my SodaStream…it’s pH 4.5!!! Wow!
It would not take many pushes of the SodaStream lever to lower my well water. Sometimes by phrasing your question you clarify your problem!

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So what you have discovered by testing your seltzer water is the exact thing you thought about in your previous post about carbonic acid. Water with an increased residence time in contact with gasses not found at atmospheric conditions will (sometimes more quickly, sometimes slowly) equilibrate to the new atmospheric conditions and absorb (or release) those gasses.

I encourage you to perform another step in that experiment and either allow your soda stream water to sit overnight or agitate it vigorously for awhile (be careful if it is contained with a lid). You will find that the pH of the water will increase again to a similar level as the carbonic acid is released as CO2 back into the atmosphere.

We test for similar conditions in some of the mine water we treat. There are actually some sites with such reducing conditions that the water actually fizzes like your sodastream as it comes out of the ground from all the CO2 it absorbed underground.

It is possible that some sort of reaction is occurring. Is it possible that your well water is ALSO in reducing conditions underground, not in contact with the atmosphere and it releases CO2 into the atmosphere, thereby increasing the pH? Or is there enough alkaline material like calcium carbonate present in your water which reacts with your acid and acts as a buffer to make your water net alkaline? I bet that is the most likely scenario. You may want to get your water tested in a lab to check if this is an ongoing challenge you wish to address. Or, you could try adding additional vinegar for a few days and see if it equilibrates eventually. Or you could try sulfuric acid or lemon juice or something else.

Yes that is definitely it - water IS high in calcium carbonate.

Great idea. Sure would be interesting if vinegar added to water eventually reaches an equilibrium. I also want to try the commercial product, ‘pH Down’, to see if can maintain a reduced pH over time.
Thanks for brainstorming!

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Very happy to help. You are attempting the opposite of what I do at work. We use limestone and other things to increase the pH of acidic mine water so it doesn’t destroy the local waterways. Please tag me if you have any other questions!

Regarding pH down, it is likely just some other acid. I’d check to see what it is and see if you can find it cheaper in another form (I bet you can).

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I moved from a place with granite rock to one with limestone. The soil pH in both places is about the same, 6.5, because over time organic material breaks down and lowers the pH. But my well goes strait through the limestone, and the well water shows it. Any evaporation leaves a good crust of minerals, much of it calcium carbonate. In fact, the calcium is mined by a Swiss company because it’s so pure. Maybe you brush your teeth with it !

So I collect all the rainwater I can and use it for all watering. In the house we don’t have a softener (it adds salt to the water, even worse for plants than calcium) so I have a separate storage for watering plants. We use vinegar to remove the calcium buildup on cooking pots. I think I’ll be OK for bone strength as I age, and so far no kidney stones. The key for personal consumption is to stay hydrated so your body can keep dumping the extra minerals. Much the same for plants, but the minerals may accumulate if the soil doesn’t drain fast, so balancing that means adding acid mulch materials.

My blueberries are slowly coming around as I mulch with pine needles and peat moss,and use only rainwater. I tried adding sulfur, and diluted phosphoric acid (sold by the gallon for etching metal and removing rust. I get it in the paint section at a big box store). I couldn’t get a reliable pH reading, but I think I might have overshot. Now the bushes are coming back.