The balancing tank is essential to the operation of an overflow swimming pool, but you will become its slave without pool water levelers!

What Is The Balancing Tank Used For?

This equipment is absolutely not necessary in a regular pool with skimmers, since the water is sucked directly into the pool.

An underground or semi-underground vanishing edge pool needs a tank called a balancing tank or catch basin to work correctly. In an overflow pool, the water exits the pool by spilling into a gutter connected to the surge tank. This channel is located on one side of the pool or the perimeter, placed lower than the edge level.
The pump sucks the water through a drain installed at the bottom of the tank and sends it into the pool through the hydraulic filtration circuit; this creates the overflow!
Without this small catch basin, the pool would not overflow. Imagine a vessel full up to the top; if you add one gallon of water to it, it overflows, and the water drains out. The principle is the same. The tank contains the volume of water needed to create the overflow blade, which is about 2 mm thick, and also compensates for water losses due to evaporation or other causes.

Outside the filtration operating hours, the addition of water from the balancing tank is no longer possible; this explains why a swimming pool does not overflow if the filtration pump is stopped.

Why Do We Need To Control The Water Level?

External events can cause the water level inside the balancing tank to vary. In some cases, the consequences can sometimes be severe.

  • The balancing tank, the swimming pool, a pipe… or all three, can leak, which causes the water level in the balancing tank to drop. Without low safety, the pump will continue to want to suck and will eventually burn out due to lack of water. It is therefore important that a system allows the pump to be stopped and possibly be automatically leveled.
  • At night, dirt in the check valve can leave it open; the pool water will fill the balancing tank. When the water reaches the overflow of the catch basin, the pool can be partially or completely siphoned off according to the level of the balancing tank. This classic problem can be avoided by a high safety device that will start the filter pump when water is to be drained off, outside the hours programmed by the clock.
  • It rains, and the water level in the pool and therefore in the balancing tank rises. Another possible safety feature is to send the water to the drain so that the filter pump does not run unnecessarily.
    A higher than usual number of bathers can also have the same effect as rain.


Without regulation, the balancing tank is a simple water tank that will not perform its function correctly and will force you to manually maintain the water level. The installation of pool water levelers prevents, among other things, your pump from burning out or your water consumption from exploding.

Now that we understand the importance of water, the installation of a regulation system must be viewed from both an economic and an ecological perspective.

Morana's advice 👇

Choose a reliable water level regulation system

If you are planning to have a pool built by a professional, ask him what type of control system he will use. Find out if it is a good fit for you.

Pick a sensor box that fits your needs.

The type of sensor box you select should be determined by whether you reside on the property. For instance, a 3-sensor box protects the pump during a water shortage, but does not prevent pool siphoning.

We help you design your infinty swimming pool

The Different Balancing Tank Control Systems

No matter which system you choose, it will, of course, be installed in the balancing tank. It is of course necessary whichever type of overflow, zero deck level, or infinity edge.

The flush type float

This is the most basic item. It will have the effect of controlling the water supply if a shortage. It will work just like a toilet. No electricity, no electronics, just a simple water supply.

This model, although basic, has a major disadvantage. It does not stop the pump, which will continue to work even if the water is not supplied for one reason or another: the water is cut off, the valve is inadvertently closed, etc.

The electric floats

This is a significant improvement on the first system, which electrically controls both the water adjustment and the pump operation. If the water level is too low, the pump will be stopped for safety reasons. The first float controls the opening of the water supply solenoid valve. This valve is closed after filling, and the pump is restarted when there is sufficient water in the reservoir.

A second float prevents the loss of water at night, in case the check valve is blocked in the open position. It restarts the pump to prevent the pool from siphoning off and will let you know that you must clean the defective no-return or check valve.

More elaborate than the first one, but not managing the automatic emptying of the tank in case of rain, this system is generally sufficient for many private overflow pools with a well-designed balancing tank.

Control Sensor Box

  • A box must be installed in the technical room and connected to the panel control of the installation. It controls the probes installed in the balancing tank.
  • From three to seven probes, can be positioned in the catch basin, to manage the different water levels.
  • A solenoid valve allows the automatic opening of the water supply in case of too low water level in the surge tank.

The more probes you have, the easier this set will make your life.

Sondes régulation bac tampon
Operation of different balancing tank control units depending on the number of sensors

Note: on some models, the 5-sensor box simultaneously stops or starts the pump and opens or closes the solenoid valve.

The “Bulleur” : The regulation without sensor

Manufactured and marketed by the French company Regul’Electronique, this new system called “Bulleur” works without a probe or float. The calculation of the water height is done by measuring the pressure and the accuracy of the measurement is ± 1 cm. The parameters are adjustable using a potentiometer located on the control box installed in the pump room.  An LCD screen permanently displays the water level in the balancing tank, so that the correct operation of the balancing tank can be checked at any time.

This device is capable of managing 5 levels.

New-generation balancing tank control system

How Do You Choose A Water Level Controller?

The main criteria for selecting a pool water level controller are the tank’s size, whether you are permanently present, and, above all, whether you want to get rid of a chore. You must also consider your budget. But the price of this equipment may seem derisory compared to the cost of a gallon of water in some parts of the world.
A simple flush float costs a few euros, electric floats a bit more, but a set of probes costs more than $500 and more than $1,100 for the last one! So it’s up to you to see which system is best suited to your situation.


Water is a precious resource that must be protected at all costs. There are still some infinity edge pools that are not equipped with surge tank regulation even today. As with the pump or filter, this equipment should be included in the basic installation.Including surge tank regulation as part of basic pool installation ensures efficient water management and conservation. It not only prevents water wastage and maintains the pool’s water level, but it also reduces strain on the water supply system and promotes sustainability. By incorporating surge tank regulation from the start, homeowners can enjoy their infinity edge pools without worrying about excessive water loss or environmental impact.