Sodium Hydroxide works well
I bought 16 quarts (4 gallons) of Sodium Hydroxide (NaOH) to save some shipping costs. From the day I ordered the chemical until I received it was 6 business days before I received the product. When I opened the box, all of the 16 quart bottles were upside down according to the arrows printed on the outside of the box. Fortunately there were red caps to seal each quart bottle so no leaks. Once I poured all of the bottles into my chemical tank and added the water, the pH was correct without adjustment. If I were to order again, I would make sure I had 2 weeks or more from the order date.