Problem with Ph down?

I bought some Ph adjuster down from the pet store and read around that it usually only takes one drop to lower the ph by like a point, however, I had to add 40 drops to 2 quarts of water to lower the ph from 8.5 to 6.5. I used both a water ph test and then i stuck a cheap ph meter in the water after adjusting, both said it was around 6.5 so I can't imagine it's wrong. How is that possible that it took 40 drops to alter the ph that much though? Is my water just really hard, and will this affect the growth of my plants?

Sounds like dodgy Ph down to me. Hard water cannot stop the work of phosphoric acid!

My fishtank ph up and down say 5ml per 10 gallons.. I use about 1/4 a ml to get a gallon of my water from about 5 to around 6.5

it contains sulfuric acid and sodium bisulfate, no phosphates. Is this the problem? Is this bad?

That sounds like a lot to add to make it go down! I normally only have to add 4-5 drops to get my water to the correct ph. I can't imagine your water is that alkaline to have to add that many drops.
But if you used two methods of testing the ph then it must be right but i'm not 100% sure about that.
Wait and see what other people say.
Peace

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i tested it with vinegar and one teaspoon of vinegar in 2 quarts lowered it from 8.5 to like 5, so I think my ph down might just be really lame. It's called ph adjust down by nutrafin if anyone has any insight?

becareful with your PH spikes...try to slowly move the pH back to normal..i would wait till tomorrow to mess with it anymore..

wolfensan said:

becareful with your PH spikes...try to slowly move the pH back to normal..i would wait till tomorrow to mess with it anymore..

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Right on. If possible start with a new batch of water - if you have nutes in it from before they will become suddenly available and burn the plants when you lower the pH. Use 1/4 nutes, and check the pH AFTER anything is added to the H2O.
I use white distilled vinegar for pH down. In my water 5 ml lowers a gallon by few tenths, like from 6.6 to 6.3.
Again, Wolfensan is 100%- go slow or you can lose the crop. I lost 24 AK-47 @ 3 wks veg over the winter, and I'm still trying to catch up!

They are in soil so although I changed the ph of the water by 2 whole points, the run-off changed to exactly where I wanted it, at 7, which was only a decrease of about a half since the soil ph is about 7.5 (which is my problem). No nutes yet, still just babies Thanks for all your input though guys.

You want a brita water jug to filter your water.. this also will lower your PH.
My tap water is about 9 and after filtering it it is about 4.5 I then use ph-up and bring it to 6.5 I was having all kinds of trouble with my plants untill I started filtering it (huge diffrance) My plants healed and went from an awful yellow to a deep green (never use your hot water tap as its full of shit).