Not recommended. Acetic and citric acid don’t hold pH like mineral acids (phosphoric. sulfuric, nitric).
They also become food for bacteria. Bad for your reservoir.
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Growing in soil, bacterial action does degrade the strength of the acetic acid over time but afaik as long as I’m regularly adjusting the PH with acetic acid when I water it should be fine?
The only time I skip adjusting with acetic acid is when I’m feeding with FPJ/FFJ and OHN as the PH of those is already around 3.0 to 4 and does the adjusting for me.
My soil runoff has generally been in the 6.3 ish range when I bother checking.
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I’ve been using citric acid for pH down (tap water, 8.0) for years now.
The thing is always test the pHed water, don’t take it for granted just because the last 10 times 1.5 mL ‘did the trick’… Trust but verify.
Cheers
G
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If needed.
These type are portable and effective. Mix nutes… then adjust PH as needed works for my coco. Ph down. My tap is great, but inconsistent.
https://www.amazon.com/gp/aw/d/B00LKF09IW/ref=psdcmw_13397611_t1_B07NNVC45T
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Has anyone used white vinegar to lower pH?
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Sure, but its isnt as effective - meaning it takes more and doesnt seem to last long. Also relatively pricey compared to battery acid.
Plus its not good to use in hydro situations as its organically based = feeds bad bacteria.
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I should have stated this would be for soil. My other option is pH down. Right now the tap water is between 7 and 7.5.
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These folks have convinced me 
I have officially given up using lemon juice and have moved to Phosphoric (pH down)…
7 ~ 7.5 is very nice…
Cheers
G
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White vinegar will work for soil in a pinch yeah, I found a capfull or less in 8-10 litres would drop ph about a point
If I am using tap water, I should let it sit overnight to let the chlorine dissipate?
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24 hours is always good yes
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It’ll take a lot longer than sitting out overnight to dissipate chlorine from water… it’ll take about a week or so for half the chlorine to dissipate.
The pH of your tap water is fine for soil growing. I used tap water with a pH of 8.1 for more than three decades to grow cannabis with no problems at all.
In soil, water pH is a lot less of a problem than it is in hydro.
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7-7.5 isn’t bad at all for soil. A little higher is better than lower. Most commercial potting mixes tend to be slightly acidic to be compatible with most people’s tapwater. How many people adjust pH for their houseplants?
Don’t use vinegar, use sulfuric or phosphoric acid. Both incredibly cheap.
Your water may contain chloramine, which will not evaporate.
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So I will test pH of the runoff before making any adjustments.
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