Balancing Tank

When an object is immersed into a container of water, the water level rises. And when a swimmer enters a pool, the water level can rise over the side of the pool. This is called water displacement. But where does that water go?

In a deck-level pool, displaced water overflows into a grate that surrounds the lip of the pool. The water collected in this grate is stored in the balancing tank. When the swimmer exits the pool, the water from the balancing tank flows back into the pool.

Also known as a surge chamber, the balancing tank should be large enough to contain the water displaced by an active swimmer, approximately 20 to 25 gallons per person. Excess water in the balancing tank can overflow into the sewage system.

When a large number of swimmers are expected to enter the pool at one time — during a swim meet, for example — the overflow return lines should be restricted with throttling valves, holding the surplus water in the pool. Otherwise, you risk overflowing the balancing tank and wasting water.

When water is added, pool water should not be allowed to flow back into the domestic line. One way to avoid this scenario is by adding make-up water to the balancing tank, maintaining a six-inch air gap. In an infinity pool, the balancing tank is used to store water needed to maintain the water level. When water is lost due to evaporation or displacement, water can be added from the balancing tank via an automatic pump.