Place 1 tsp. of baking soda into a 1L plastic bottle filled with water. Shake the water so that the baking soda completely dissolves. Dip your pH strip into the water. Record the color. Examine the pH color guide that came with your pH strips. Find the color that matches the color obtained. Read the associated number. Record alkaline if the number if greater than 7, very alkaline if it is 8 or 9. And record extremely alkaline if it is above 9.
Reduce the alkalinity level by adding one drop of vinegar. Dip a new pH strip into the water solution and note the color of the pH strip. Record the pH level by cross-referencing the pH color code. Write down acidic if the pH is below 7 and alkaline if it is above 7. Check the new pH to confirm that it is lower than the original water solution with baking soda.
Add small amounts of baking soda, 1/8 tsp. at a time, and measure the alkalinity with the color strips. Keep adjusting the pH by adding baking soda and vinegar until you obtain the pH level you desire.