The term "pool hydraulics" refers to the water circulation system in swimming pools. Good swimming pool hydraulics guarantee the correct distribution of disinfectants. Hydraulics not only includes the economical skimmer system to remove water from the surface, but also the more effective overflow system in swimming pools. From this overflow system, the water is led by water jets over the edge of the pool into an overflow channel, from where it enters the overflow tank. This tank is designed in such a way that when the pool is in use, the tank can contain the amount of water being moved. When the pool is not in use, it has enough water stored for back washing.