—Pumps, filtration and plant
Balance tank design
Overflow pools need somewhere for the water to go. The balance tank is that place, and its size and controls decide how well the pool behaves.
In an overflow or infinity edge pool, water spills over the edge into a channel or basin and flows to a balance tank. The circulation pump draws from the tank, through the filter and equipment, and back into the pool. The tank must hold water displaced by swimmers, water in transit in the channels, and enough reserve that the pump never runs dry.
Equipment guides are about choosing, sizing and installing plant, not about day-to-day pool care.
Sizing depends on pool area, expected bather numbers, channel volume and evaporation. Level controls manage automatic top-up and protect the pump. The tank needs access for inspection and cleaning. Getting the design right avoids overflows, pump starvation and wasted water.
01Summary
What matters most here
Holds displaced water
From swimmers and channels.
Feeds the pump
Never letting it run dry.
Controls the level
Top-up and overflow.
02Detail
Design factors
Displacement
Water pushed out by swimmers.
Channel volume
Water in transit around the edge.
Reserve
Minimum level for the pump.
Level control
Sensors and automatic fill.
Access
For inspection and cleaning.
03Before you start
When designing
Estimate bather numbers
For displacement.
Plan tank location
Near the plant.
Specify controls
Level sensors and alarms.
—In practice
How to use this
Work out the tank volume needed for bather displacement, water in transit in the channels and a reserve for the pump. Plan level controls, top-up and overflow arrangements, and access for cleaning and inspection. Size the pipework from the channels to the tank for peak flow, when many people enter the pool at once.
Mistakes worth avoiding
- An undersized tank
- A tank that is too small overflows when bathers enter, or runs low and lets the pump draw air when they leave.
- No access for cleaning
- Balance tanks collect debris and need inspection. A tank that cannot be reached is a tank that is never cleaned.
04FAQ
Common questions about this
- Why does an overflow pool need a tank?
- Water constantly leaves the pool over the edge; the tank collects it.
- What if the tank is too small?
- It can overflow when swimmers enter or run low and starve the pump.
- Does the tank need cleaning?
- Yes, periodically; access is important.
- Is it the same as a catch basin?
- Infinity edge basins can act as the balance reservoir, sized the same way.
05Read next
More pool guides on this
- Keeping pool equipment quietMore on the equipment that keeps the water moving.
- Pool circulation and returnsMore on the equipment that keeps the water moving.
- Sand, glass or cartridge filtrationA related choice between two options.
- Single-speed or variable-speed pumpA related choice between two options.
Filed under pump & filtration systems. Every pool guide is listed on the pool guides page.
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Designing an overflow pool?
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