pH is the acid/alkali balance in the water and is a logarithmic scale. 

pH 7 is neutral. 

pH 6 has 10 times more acid (literally hydrogen ions) in the water than ph7. 

pH 5 has 100 times and 4 has 1,000 times, etc. 

The pH of human skin is acidic at pH 5.5. 

Soda water is about pH 3.5, which is over 1,000 times more acid than neutral water. 

Going the other way, pH 8 is alkaline and 10 times more so than pH 7. 

pH 9 is 100 times. 

Importantly pH also has a large effect on the effectiveness of the chlorine sanitiser in conventional pool chemistry water.  If pH is too high, the chlorine will ‘switch-off,’ converting from hypochlorous acid to hypochlorite, and becoming up to 30 times less effective.  Said another way, you need up to 30 times as much chlorine in the water at pHs above 8 as you do at pHs around 7 with conventional chemistry.   Pools are normally operated around pH 7.4-7.6 with conventional chemistry for this reason. 

These pH restrictions do not apply with Pooled Energy’s Advanced Water Chemistry and the combined chlorine/bromine sanitiser remains effective and the water comfortable to swim, from pH 7 to over pH 9….a much wider ‘sweet-spot.’