Maintaining the right chemical balance in your swimming pool is essential for the health of swimmers and the longevity of your pool equipment. Two of the most critical factors in pool water chemistry are alkalinity and pH. Understanding why these parameters matter — and how to keep them in balance — is one of the most important aspects of pool ownership.
pH is a measure of how acidic or alkaline your pool water is, on a scale from 0 to 14. A pH of 7.0 is neutral; values below 7.0 are acidic, and values above 7.0 are alkaline. The ideal pH range for a swimming pool is between 7.2 and 7.6.
When the pH is too low (acidic), pool water can cause eye and skin irritation for swimmers, corrode metal pool equipment and fittings, damage the pool surface and liner, and reduce the effectiveness of chlorine sanitiser.
When the pH is too high (alkaline), chlorine becomes far less effective — meaning your pool is not being properly sanitised even if the chlorine level appears normal. High pH can also cause cloudy water, scaling on pool surfaces and equipment, and skin and eye discomfort.
Total alkalinity (TA) refers to the amount of alkaline substances dissolved in your pool water, primarily bicarbonates, carbonates, and hydroxides. It is measured in parts per million (ppm), with the ideal range for most pools being 80–120 ppm.
Alkalinity acts as a buffer for your pool’s pH level. Without adequate alkalinity, even small additions of chemicals — or rain, sweat, and other contaminants — can cause the pH to swing dramatically up or down. This instability makes it very difficult to maintain a consistent and safe pool environment.
When alkalinity is too low, pH levels become erratic and hard to control, the water may become corrosive, and surfaces and equipment are at risk of damage. When alkalinity is too high, the water can become cloudy, pH becomes resistant to adjustment, and scale can build up on pool surfaces and inside pipes and equipment.
Alkalinity and pH are closely linked. Getting the alkalinity right first makes controlling pH much easier. Think of alkalinity as the foundation — once it is in the correct range, pH becomes more stable and manageable. For this reason, pool owners and technicians always adjust total alkalinity before adjusting pH.
Testing your pool water at least once a week is recommended, especially during heavy use or after heavy rain. Use a reliable pool test kit or take a water sample to your local pool shop for analysis. To raise alkalinity, add sodium bicarbonate (baking soda). To lower alkalinity, add muriatic acid or dry acid carefully and in small increments. To raise pH, add soda ash (sodium carbonate). To lower pH, add muriatic acid or dry acid. Always follow the product instructions and add chemicals with the pump running to ensure even distribution throughout the pool.
Keeping alkalinity and pH within their ideal ranges is fundamental to a clean, safe, and enjoyable plunge pool or swimming pool. Proper balance protects your investment by preventing corrosion and scale buildup, keeps your sanitiser working effectively, and ensures a comfortable swimming experience for everyone. Regular testing and prompt adjustments are the key to achieving and maintaining this balance.
