How Do I Change Swimming Pool Alkalinity?

Purchase a pH test kit from your local pool supply store. Follow the instructions on the kit to establish the water’s alkaline level. Determine if the alkalinity is too high or too low by checking the kit’s pH chart. Typically, the desired alkalinity range is between 80 and 150 parts per million (ppm), which should stabilize the pH level in the neutral zone of between 7.2 and 7.8.

If the alkaline level is too low, or below 7.2, add 9 lbs. of baking soda for every 10,000 gallons of water to raise the alkalinity in the pool. Stir the baking soda in a bucket with enough water to create a pourable, lump-free mixture. Pour the alkalizing solution into the pool. Scrub the bottom of the pool with a pool brush to disperse the baking soda and dissolve any remaining granules. Warehouse or big-box stores usually sell oversized products; alternatively, find bulk baking soda in the bulk products section of a local grocer.

Check the pH level of your pool water again in two days. If the level of alkalinity is still low, add another 6 lbs. of baking soda per 10,000 gallons of water, as recommended by the Arm and Hammer website's "Pool Owner's Guide." This should bring the alkalinity into the neutral range for several weeks, but check the water each day that you plan to use the pool to maintain the balance.

If the alkaline level is too high, or above 7.8, add hydrochloric acid to your pool’s water. Purchase an appropriate acid product from your local pool supply store and add as directed. PoolCenter.com suggests “pooling” the acid by adding it at the bottom of the deep end with the filter shut off to allow a slow distribution.