The total alkalinity (TA) in the hot tub is what helps the pool sustain a good pH level and resist change to the pH level. The pH needs to be in the range of 7.2 to 7.8, but the ideal is 7.4 to 7.6. Alkalinity in the hot tub is controlled by using pH increaser or pH reducer to obtain the ideal range of 80 to 120 parts per million (ppm).
Test the hot tub water with the test strip for total alkalinity. The strip is placed in the water and pulled out. The test strip will change colors. Compare the test strip to the color chart in the kit. It will tell you if you need to lower or raise the TA in the hot tub.
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Lower the TA using sodium bisulfate. If you need to lower the total alkalinity in a hot tub with 1,000 gallons of water, use 0.21 lbs. to lower the TA 10 ppm, 0.43 lbs. to lower the TA 20 ppm, 0.64 lbs. to lower the TA 30 ppm and 1.06 lbs. to lower the TA 50 ppm. Sprinkle the powder in the hot tub around the edges.
Raise the total alkalinity using sodium bicarbonate. Raise the TA in a hot tub with 1,000 gallon of water using 0.14 lbs. of sodium bicarbonate to raise the TA 10 ppm. If the TA needs to be raised 20 ppm, use 0.28 lbs. of sodium bicarbonate. For 30 ppm, use 0.42 lbs. Use 0.56 lbs. to raise the TA 40 ppm or 0.70 lbs. to raise the TA 50 ppm. Sprinkle the powder in the hot tub around the edges.
Retest the hot tub water 24 hours after adjusting the total alkalinity. If the TA needs adjusting, readjust the chemical balance. After the TA is in range, test the pH levels with pH test strips and adjust the pH if needed.