POOL WATER CHEMISTRY 101.. pH and it’s effect on your water.
Is pH really that important?
Your pH is one of the most important factors in pool water balance and it should be tested and adjusted on a weekly basis. Simply put.. pH is the measure of how acid or alkaline your swimming pool water is. It is also frequently described as the amount or strength of the hydrogen in the water. A pH of 7.0 is neutral.. below 7.0 is acidic & above 7.0 is alkaline. You should always try to keep your pool’s pH within the range of 7.2-7.8.
What happens when the pool is too acidic?
(pH is low):
1. If your swimming pool is plaster, the pool water will begin to dissolve the surface, creating a roughness, which is ideal for pool algae growth. A similar result occurs in the grouting of tiled swimming pools.
2. Metals corrode – and this includes swimming pool equipment, pipe fittings, pump connections, etc. As the swimming pool walls and metal parts corrode, sulphates are formed. These sulphates are released from the water onto the walls and floor of the swimming pool causing ugly brown, black or purple stains.
3. Chlorine, which is used as a disinfectant in the swimming pool water, is activated and lost to the atmosphere very quickly. The water is not being sanitised, and we are throwing away our money by adding chlorine when the pH is too low.
4. When we swim, our eyes and nose burn. Our swimwear fades and perishes. Our skin gets dry and itchy.
What happens when the pool is too alkaline?
(pH is high):
1. The calcium in the swimming pool water combines with carbonates and forms scale, just like in our kettles. This calcification is seen most at the waterline, where it traps dust and dirt, turning black with time.
2. The swimming pool water starts to become cloudy or murky and it loses its sparkle. Catch yourself buying clarifier frequently? This could be the result of your pH being too high.
3. The calcium carbonate has a tendency to plate out on the sand in the swimming pool filter, effectively turning it into cement. So your filter becomes a cement filter, and loses its ability to trap dirt and other debris from the pool water.
4. As the pH rises, the power of the chlorine to act on foreign particles is lost. At a pH of 8.0 the pool can only use 20% of the chlorine you put in. So 80% of it goes to waste and you would need 5 times as much chlorine to provide the disinfection you need.
5. In alkaline swimming pool water, the swimmers suffer too. Our eyes and nose burn and our skin gets dry and itchy.
I truly hope this information was beneficial. If you have any questions or you’re experiencing further issues please don’t hesitate to shoot me a quick email at
February 17th, 2011 at 12:27 am
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