Although I am still waiting on my Tower Garden to ship, I have been doing hydroponics for a few years. I have the same issue with my well water about 8.5 at best. Dropping the PH from this high requires large doses of something to lower it. Keeping the answer simple, adding this much 'extra stuff' to the water makes it hard to maintain PH as well as (in my experience) making nutrient availability an issue.
The solution for me was reverse osmosis water. I have a unit in the kitchen for drinking water. I installed a second unit connected to a garden hose in my greenhouse. Although it only makes several gallons a day, I have 55 gallon barrels that I collect the water into. I use this water to make or top off nutrient solution. The RO units are available at big box stores for $150 - $225.
I also collect and use rain water to use in my outdoor garden as my plants respond to it better than the high PH well water. This might be a better option for you. Some people use the 5 gallon refillable plastic jugs and get water from the store if all they need is 25 gallons. Hope this helps.
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Hi jjsfarm, A high output Reverse Osmosis (RO) filter will be your best option. Here is an example of one: https://www.amazon.com/Hydro-Logic-Stealth-Reverse-Osmosis-Filter/dp/B01MYVS35X/
BTW... If your water source is from a municipality (a.k.a. city tap water) and it has a pH of 8.5, I would strongly advise that you report it to your water utility company (8.5 is way out of spec).