Dont use that crap.... I learned the hard way....... If I were you, I would use Dynagro base nutes, as it's a good nute for hard water, as it lowers the ph perfectly, as I also have 8.9ph tap water(high) and it lowers it.... But, yea... If you're going with an other, just get PH DOWN..... NOT ONLY is Vinegar gonna make your weed gonna taste like absolute CRAP..... But it also invites alot more pests into your grow medium..... Dont do it... Spend those extra 20 bucks on a ph kit like said... Amazon has them for like 16-18 bucks with free shipping, and it is super concentrated and will last you a long time...
An other thing I would suggest is to buy an RO system...... You can get one for as cheap as 50-60 bucks w free shipping from this place called Purewaterclub.com..... They turn my super alkaline water into perfect 6.2.... I just add 2 drops of ph down per gallon if i'm watering with pure water... or sometimes just water just like that, as it wont hurt....... But you'll have to get yourself some Cal Mag for it, as all water needs calcium and Magnesium for solid plant growth...
Get a RO filter, man..... I promise you will love it, as you really really need it, and you'll probably double your yields vs the junk water you have now....... at over 10.0 ph, it is most likely over 600ppm already, as mine was just under 500ppm at 8.8ish...
and those RO systems are so cheap at 60 bucks, I'm not even gonna bother replacing the filters for nearly 35 bucks every year..... I'm just gonna buy a whole new system, as the old one will still work for plants and ppm way lower than 100ppm by that time, but no longer the guaranteed 0ppm or whatever for the first 6 months to a year....... Mine got as clean as 3ppm, and after 2 months of daily use, it's at 7ppm right now..... Not bad, as it promises 0ppm for water under 3-400ppm, but mine was near 500..... It will probably clean yours to around 10-15 ppm, which is still great....
I'll use second RO system for drinking/cooking, and continue using my second till it it doesnt clean my water under 100ppm any longer.... THEN maybe I'll buy it filters.... But I'll never drink water over 20ppm..... It actually does make my tap water taste good..... I didnt believe it would