Baking soda vs soda ash for pool alkalinity: Baking soda wins for low-alkalinity pools without spiking pH

Baking soda raises total alkalinity without jacking up pH the way soda ash does. Use 1.5 pounds per 10,000 gallons to bump alkalinity by 10 ppm — dissolve in water first, pour in deep end with pump running. Test after six hours; overshooting locks pH in place.