This alkalinity will usually be present as bicarbonates, but with a very high pH carbonates and hydroxides can be present as well. It would require a much greater force if the sphere had the bulk density of a cannon ball. In this example, the increase in bulk density between the balloon and the cannon ball is analogous to an increase in alkalinity. The increase in force required to move the balloon and the cannon ball is analogous to the idea of increased 'buffering'. It is important to create the correct amount of buffering in the pool such that the pH can be adjusted if necessary but rapid fluctuations are prevented.
Low alkalinity can result in corrosion and discomfort to bathers.
Free chlorine plus combined chlorine . This apparent contradiction in terms refers to conductive chemicals that can accumulate in the pool particularly when the water evaporates, or when the pool is not 'diluted' with sufficient fresh water. They are mostly made up of chlorides and sulphates. Chlorides can accumulate with long term use of sodium hypochlorite. Another stabilised chlorine donor.