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January, 2013

Adjusting pH & Alkalinity In Spas

David Jewell - Spa Parts Plus

By David Jewell - Spa Parts Plus

AquaChek Spa pH Tester - Spa Parts Plus

pH and Alkalinity are related and they affect each other in your spa water. They are relatives because they are measures of similar conditions.

pH is the balance between positive hydrogen ions (H+) and negative hydroxide ions (OH-) in the water. Alkalinity is the measurement of the amount of carbonate, bicarbonate and hydroxide ions (OH-) in the water. Since alkalinity measures one of the factors used in pH, you can see how it is related with pH levels and how they might affect one another.

If pH and alkalinity are not in balance, there is slow, general damage to the spa equipment. Pump seals, heaters, spa covers, and jets are all susceptible to damage from pH and alkalinity imbalances.

Alkalinity First!

Alkalinity, briefly stated, is the capacity of water to neutralize acids. This ability is why it is sometimes called a “pH buffer”. Without a proper alkalinity balance in the spa water, pH become unstable and the pH scale can climb and fall erratically. A smart way to approach measuring spa water chemistry is to get your alkalinity stable at a proper level before you attempt to adjust pH. Normal alkalinity range is 80-120 ppm.

How do we adjust alkalinity?

To increase alkalinity, we use Alkalinity increaser, otherwise known as Sodium Bicarbonate (Baking Soda). There will be a dosage on the bottle to follow. If you are using bromine tablets your alkalinity will be generally decreasing over time; the acidity of the tablet neutralizes some of the alkalinity. If your alkalinity is generally decreasing, then it is best to adjust your alkalinity to the high end of the scale, so when it drifts down due to the bromine, it still stays in the normal range.

To decrease alkalinity, we use pH decreaser (dry acid) in larger doses than normal. To reduce alkalinity using dry acid (Sodium Bisulfate), one ounce of pH decreaser will reduce the alkalinity in 300 gallons of water about 10 ppm.

Adjusting pH

After the alkalinity is correct and stable buffing the pH, you can adjust the pH to get a correct and stable balance. Normal pH range is 7.4-7.6.

We adjust low pH using pH increaser (Soda Ash).

We adjust high pH using pH decreaser (Sodium Bisulfate).

David Jewell - Spa Parts Plus

By David Jewell - Spa Parts Plus

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