Total alkalinity is a measure of the total alkaline substances found in the pool water. For swimming pool purposes we usually determine the carbonate content of the water by measuring the level of calcium carbonate. Total Alkalinity (TA) should usually be kept at 80 - 120 ppm, though in high alkalinity waters this is often hard to achieve without resulting in an abnormally low pH. The results of a low TA may be one or more of the following:
Sodium bicarbonate (bicarb) will raise the TA without excessively raising the pH. Regular pH-up will raise the pH as well as the TA and should not be used. Care should be taken to increase the TA over a period of time, adding a maximum of 1 pound of bicarb for each 6,000 gallons of water. The bicarb can be added at this rate every 4 days, until the required level is reached. The results of high TA may be one or more of the following:
Regular small "acid shocks" with pH-down will reduce the pH while lowering the TA. This can be an extremely slow process and it may take weeks or longer to reduce high TA. One suggested method is as follows:
The above method should be used only when the pH is high and your pool requires pH-reducer. If the pH is normal, adding a shock will reduce the pH to undesirable levels resulting in further pool problems. Care should be taken not to let the pH-reducer sit for too long as it will begin etching and softening the plaster, marbelite, marcite or tile grouting. It is also recommended to dilute the pH reducer in a bucket of water before adding to the pool to prevent this problem from occurring.
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