Vinegar works in a pinch, and lemon juice isn't great for anything but emergencies. (and it's a bitch to ph test OJ if using color-coded test kits) Not sure there's anything wrong with the stuff from Lowes. Might want to do monthly flushes to release any salt build-up. (sodium sulfate and sodium bisulfates are acid salts)
Personally, my well water comes out of the tap at 7.9 to 8.0 ph. I use General Hydroponics phDown. It's phosphoric acid, and a gallon lasts a couple of years at my consumption rate. 1/4 tsp per gallon puts me in range. Breaks-down to pennies per adjusted gallon.