Pool chemistry is constantly changing. In particular, with conventional chemistry pools, pH can move out of acceptable ranges in just a day or two. Chlorine levels often drop rapidly during the day, halving in just 35 minutes in strong UV, and pH can climb rapidly in just a couple of days due to alkaline pool finishes.
Even weekly chemical adjustments cannot keep up with the constantly changing pool chemistry. This can result in inconsistent disinfection and algal blooms. You also get big swings in pH when acid is added manually and this is bad for pool surfaces and can result in sore eyes and irritation.
The Pooled Energy system monitors pool chemistry every two minutes when the filter is running, and approximately every two hours when it’s not, and it adjusts sanitiser levels accordingly. With the addition of the inherently much more stable Advanced Water Chemistry you get a much better result.
The Sydney Morning Herald in May 2013 published an article about public pools in the US. The article noted that more than half of public pools (up to 77%) in the US were tainted with human faeces based on information provided by the US Centers for Disease Control and Prevention. These public pools are all regulated and professionally maintained and could therefore be expected to be much better run than most residential pools, despite their increased swimmer loads. Other formal reports from various global health organisations paint a similar picture. You need good sensing and control to deal with such conditions>