The potential of hydrogen (pH) measures how acidic or basic pool water is on a scale from 0 to 14. Maintaining an appropriate chemical balance is one of the most important aspects of pool ownership. A reading of 7.0 is considered neutral, but the ideal range for pool water is slightly basic, typically between 7.4 and 7.6. This narrow window is necessary for swimmer comfort and for preserving the integrity of pool surfaces and equipment.
Understanding the Impact of Low pH
Water with a low pH (below 7.4) is acidic and causes costly problems for both swimmers and the pool structure. This acidic water will aggressively seek to balance itself by dissolving minerals and metals from any surface it touches. This results in the corrosion of metal fittings, such as ladders, railings, and the internal components of heaters and pumps, and causes etching and staining on plaster, tile grout, and concrete surfaces over time.
For swimmers, low pH water can be very irritating because it strips the body’s natural oils, leading to dry skin, itchy eyes, and nasal passage discomfort. Furthermore, a low pH causes chlorine to become unstable and dissipate rapidly. When chlorine is too aggressive, it is consumed quickly, reducing the water’s ability to disinfect properly. Maintaining the correct pH maximizes chlorine’s effectiveness, making the pool safer and reducing the overall chemical consumption.
How to Accurately Test Pool pH
Before adding any chemicals, you must obtain an accurate reading of your current water chemistry. A clean, uncontaminated container should be submerged elbow-deep, away from the skimmers or return jets, which can temporarily skew the results. Running the pump for at least 15 minutes before sampling helps ensure the water is fully circulated.
Liquid drop kits, which use Phenol Red, are more reliable than test strips for accurate pH measurement. The color comparison method used by liquid kits offers greater precision for determining exact values. Digital meters offer the most precise numerical readings, although they are a larger initial investment. Regardless of the method used, it is important to test the Total Alkalinity (TA) level first, as TA acts as a buffer that stabilizes the pH. The recommended TA range is 80 to 120 parts per million (ppm); keeping it balanced prevents the pH from fluctuating wildly, a condition often called “pH bounce.”
Step-by-Step Guide to Raising Pool pH
The most common and effective chemical used to raise pool pH is soda ash, which is chemically known as sodium carbonate. This substance raises the pH level quickly with a slightly lesser effect on the total alkalinity compared to sodium bicarbonate. When handling any pool chemical, it is important to wear appropriate personal protective equipment, including gloves and eye protection, and avoid inhaling any fine dust.
For general guidance, approximately six to eight ounces of soda ash are typically needed to raise the pH by 0.2 units in a 10,000-gallon pool. It is always best to check the manufacturer’s directions for specific dosing instructions based on your pool’s volume and current pH level. To apply the chemical safely, first dissolve the measured quantity of soda ash in a clean five-gallon bucket filled with pool water, adding the chemical to the water (never the reverse) to prevent a vigorous reaction.
With the circulation pump running, walk around the edge of the pool and slowly pour the dissolved solution into the deep end. Pouring into the deep end allows the chemical to disperse and mix thoroughly before reaching any pool equipment. After application, allow the pool to circulate for a minimum of six hours to ensure the chemical is completely distributed. After this circulation period, re-test the water to confirm the new pH level is within the ideal 7.4 to 7.6 range. If the target is not yet reached, repeat the process with a smaller dose to avoid overshooting the target and causing the pH to become too high.
Factors That Cause Low Pool pH
Low pH is frequently caused by external factors and the type of sanitizers used for routine maintenance. Rainfall is naturally acidic, and a significant storm can introduce enough acidic water to lower the pool’s pH quickly. High bather loads also contribute to low pH, as sweat, body oils, and other contaminants are acidic and consume the alkalinity buffer in the water.
The most common chemical cause of low pH is the use of stabilized chlorine tablets, which are made from trichloroisocyanuric acid, or “Trichlor.” As these tablets dissolve and release chlorine, they also release a low-pH acid that steadily drives the water chemistry downward. Regularly monitoring water balance allows owners to proactively counteract these influences and anticipate the need for pH adjustment.