Total Alkalinity

What Total Alkalinity Is

Total alkalinity is the measure of the amount of alkaline buffers (primarily carbonates and bicarbonates) that are present in the water. These alkaline substances buffer the water against sudden changes in pH. Total alkalinity is considered the key to water balance. It is the first parameter you should balance when making adjustments to your water.

Why Total Alkalinity Is Important

From time to time you may speak with a pool owner who has trouble balancing the pH. Maybe he complains that the pH fluctuates suddenly despite his best efforts to keep it in the ideal range. There’s a good chance that the underlying problem is the level of total alkalinity in his pool.

Total alkalinity acts as a buffer for pH. Think of the alkalinity as training wheels: it keeps the pH in balance without allowing it to tip too far to either side. Of course the pH can still drift upward or downward, but that change will happen gradually as long as the alkalinity falls within the ideal range.

We’ve stated that total alkalinity is the measure of alkaline buffers that help to prevent sudden changes in the pH. The primary components of alkalinity have the ability to neutralize acid. (Antacids such as Alka Seltzer® use carbonates and bicarbonates to neutralize the acid in your stomach!) The higher the alkalinity, the more efficient the water becomes to neutralize different acids that are introduced into the water.

If the alkalinity is too low, anything introduced to the water will have an immediate impact on pH. This is often referred to as pH bounce. Maintaining an ideal level of alkalinity will protect your pool or spa and its equipment from the harmful effects of pH bounce. (Abrupt shifts in pH can cause scaling or corrosion of metal equipment and fixtures as well as other problems.) The ideal range of total alkalinity for pools and spas is between 80 and 120 ppm (mg/L).

Total alkalinity and pH are very closely related because the ratio of carbonates to bicarbonates is determined by the pH of the water. At a higher pH, more carbonate ions are formed. If the pH gets too high, the excess carbonate tends to form scale.

If Total Alkalinity Is Low

The pH may fall, corroding surfaces, metal equipment and fixtures.
The pH may bounce around and cause problems.

If Total Alkalinity Is High

Calcium and metals tend to precipitate or come out of solution—mineral deposits may build up on the pool and equipment, staining and forming scale.
The pH can drift upward. You may have to add large amounts of acid to lower pH, and even this may not ensure that the pH will remain stable once the desired level is attained. The pH may continue to climb back up after being balanced.

Alkalinity Control

Increasing Total Alkalinity – Sodium bicarbonate is the most effective and popular chemical for increasing total alkalinity. Other chemicals that can raise the total alkalinity are sodium carbonate (soda ash) and sodium sesquicarbonate. The amount required varies from pool to pool; it depends on the chemical used.

Decreasing Total Alkalinity – When the total alkalinity is too high, you can lower it by using muriatic acid or sodium bisulfate. Sodium bisulfate is a granular product that is safe to handle and easy to use. Muriatic acid is a concentrated liquid acid that can cause severe burns in direct contact with skin.

Adjusting Total Alkalinity- If adding alkalinity increaser or decreaser be sure to do it gradually over a period of several days. Dumping the required amount into your pool will not have the desired effect. Add the product in measured doses over as many as 5 to 7 days. It may not seem like anything is happening but at some point during treatment the Total Alkalinity reading will change.

Table 2:

NSPI Total Alkalinity Standards
Minimum	Ideal	Maximum
60	80 - 120	180

Testing Total Alkalinity

Test total alkalinity a minimum of once per week. You should also test after usage of the pool or spa or after any change in environmental conditions. External factors like rain, pollen and wind-blown dust can shift the alkalinity up or down.

Because alkalinity requires such frequent testing, all AquaChek multiple-parameter test strips include a test pad for total alkalinity.