Howdy again friends! I’ve been blessed with pH levels at 6.3-6.8 range straight out of my fridge w/filter before. Now my new fridge is kicking out 7.2 water so I bought this 
. It only takes a single drop per gallon to get back to 6.7 but just noticed the “Sulfuric Acid” part that’s safe for plants but not sure if that includes plants you smoke?? Any thoughts?
Many pH down products us phosphoric acid. I can’t imagine that sulfuric acid is a problem if used in a commercial product. Any pH down product you use is going to come in the form of some kind of acid. It’s unavoidable.
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You are good. 
Sulfuric acid is slightly stronger acidifier, but not by much. So you may need to use less for comparison.
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And if you don’t want to use that stuff, I lower mine a little with citric acid you buy in the canning section in the store. A little bottle last a long long time. A lot cheaper that ph down liquid.
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This from the good ol’ internet:
Sulfuric acid (from 20 to 98% pure) : This acid is commonly used in car batteries and offers the largest pH dropping ability per unit of volume among all the strong acids. It is however important to use food grade sulfuric acid in hydroponics as normal battery acid can include some metallic impurities – from the fabrication process of sulfuric acid – that might negatively affect a hydroponic crop. Food grade sulfuric acid is safe to use in hydroponics. A big advantage is that plants are quite insensitive to sulfate ions – the nutrient provided by sulfuric acid – so adding sulfuric acid does not really affect the nutrient profile being fed to the plants. Note however that most battery acid products in developed countries are also ok, as the quality of these acids demands the metallic impurities (more commonly iron) to be quite low. If in doubt, you can do a lab test of the sulfuric acid to see if any impurities are present.
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Yep, don’t buy the sulfuric acid for ph down from ORileys auto parts.
The API stuff in the photo of @Jerdan03 posted is good to go. It’s for aquariums and the fish are more sensitive than us to metal impurities. I would say the API fish product is as clean or better than food grade. I ise API products in my work aquariums all the time. It’s a clean quality product.
I would not use it for gardening unless I had really hard water to ph down; and honestly then I would plan to go RO eventually….
I am a fan of the citric acid or fresh citrus juice for ph down myself. I have also been known to use a little Red Bull or coke if I am in a pinch and out of lemons. Baking citric acid is an excellent tip. Thank you @Dexterado that is the money shot.
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Yeah, I’ve used it for years. And still like only on my second bottle :). Funny you mentioned O’Reilly, I retired from there.
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Yes, only 1 tiny drop per gallon takes it from 7.3-6.8!