Total alkalinity is the sum of all the alkaline substances in the water. The acceptable range for total alkalinity depends on the sanitizer you use. For example, the ideal range

When to Drain

Because of heavy bather loads and the constant addition of chemicals, spa water can take on a high concentration of dissolved solids, making the water difficult to balance. To ensure water quality and keep the water easy to balance, drain the spa water at least every three months more often if the spa is used heavily.

To better determine how often you should change the water, use this formula:

spa size in gallons -f (number of daily bathers x 3)

= number of days between water changes


If you have a 500-gallon spa that’s used by two people every day:

500 v (2 x 3) = 500 * 6 = 83

You should change the water every 83 days, or every 2 to 3 months.

Between drainings, you can reduce the contaminants (body oil, dirt, lotions, deodorants, makeup, hair products, etc.) in your spa water by having bathers shower before entering the tub.

for total alkalinity when using bromine (the most popular spa sanitizer) is 100 to 120 parts per million (ppm).

Maintaining proper total alkalinity levels is important because it helps to lock in (or stabilize) pH. In other words, once you have total alkalinity under control, pH will tend to remain constant. In contrast, if alkalinity levels are too low, you’re likely to see wide fluctuations in pH.

Testing Total Alkalinity. The same test strips or kits you use to test pH will often measure total alkalinity, too. Be sure, however, to follow the testing guidelines on the packaging, as procedures often differ from one brand of test strips or test kits to another.

Adjusting Total Alkalinity. To raise total alkalinity without raising pH significantly, add sodium bicarbonate (often referred to as baking soda) to the water. If you also want to raise pH, you can use sodium carbonate (often referred to as soda ash), which is a more alkaline chemical compound. If your source water is extremely hard (meaning it contains high levels of calcium and magnesium), it’s possible that your total alkalinity levels may be too high. Hard water is not necessarily a problem if pH can be brought into the acceptable range and the water remains clear. Use a pH decreaser or liquid muriatic acid to reduce total alkalinity. Be sure to follow the manufacturer’s instructions when applying any spa chemical.


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