Balance tanks are designed to ensure that the water in the pool remains at the correct level. In pools with a deck-level surface water drainage system, a balance tank is essential. This is because in a deck-level pool, the pool water is constantly overflowing at the surface into the drainage channel. If, for example, 50 people got into an empty deck level pool at the same time, an equivalent volume of water would overflow into the drainage channels. If those 50 people then all got out straight away, the pool water level would drop significantly and water would no longer be overflowing into the drainage channels, thus disabling the functionality of the surface water draw-off system, which is to remove the pollution at the pool water surface. Pools with scum trough and skimmer surface drainage systems don’t always have a balance tank, but those that do will enjoy much better water quality.
Balance tanks also enable the backwashing (discussed later) of the filters to take place without it having an effect on the pool water levels as the water in the balance is used to carry out the backwash, rather than the water in the pool. Balance tanks operate in a broadly similar way to a toilet cistern. When a toilet is flushed, the cistern (balance tank) empties and then get re-filled with fresh water until it reaches the ball-cock valve at the top of the cistern that automatically shut off the fresh water supply valve.
Swimming pool balance tanks need to be emptied and cleaned on an annual basis, with spa pool balance tanks requiring cleaning on a weekly basis. Swimming pool balance tanks should be regarded as confined spaces and therefore, a ‘permit to work’ system should be used to ensure that the job is undertaken safely.