What is the balancing tank used for?
This equipment is absolutely not necessary in a skimmer pool since the water is sucked directly into the pool.
In an underground or semi-underground overflow pool, a tank, called a balancing tank, is placed on the filtration circuit between the outlet of the overflow gutter and the pump; the pump sucks the water through a drain located at the bottom of the tank and sends it into the pool through the hydraulic filtration circuit; this is what creates the overflow!
Without this tank, the pool would not overflow. Imagine a basin full up to the top; if you add a few litres 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 of 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.
You are interested in an overflow pool and want to know more about the role of the balancing tank.
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 serious.
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 to be auomatically levelled.
At night, dirt in the non-return valve can leave it open; the pool water will fill back the balancing tank. When the water reaches the overflow of the buffer tank, 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 upon 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 normal 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 properly and will force you to manually ensure that the water level is maintained. The installation of pool water levellers avoids, among other things, your pump from burning out or your water consumption from exploding.
The different balancing tank control systems
Whichever device is chosen, it will, of course, be installed in the balancing tank. It is of course necessary whatever the type of overflow, zero deck level or infinity.
The flush type float
This is the most basic system. It will have the effect of controlling the water supply in the event of a shortage. It will work just like a toilet. No electricity, no electronics, just a simple water supply.
This model, although very simple, 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, …
The electric floats
This is a significant improvement on the first system, which electrically controls both the water adjustment and the pump operation. It will stop the pump for safety reasons when the water level is too low, open a solenoid valve for the water supply, close the it and restart the pump when the water level is sufficient.
A second float prevents the loss of water at night, in case the non-return or 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 dimensioned balancing tank.
Control sensor box
They consist of:
- A box installed in the technical room and connected to the panel control of the installation. It controls the probes located in the balancing tank.
- A minimum of 3 and a maximum of 7 probes, can be positioned in the balancing tank, in order to manage the different water levels.
- Solenoid valves for automatic opening of the water supply in case of low level or for emptying the tank in case of rain or other.
The box with 3 probes only covers only the eventuality of a lack of water while the one with 7 probes will allow to manage all mentioned situations.
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 by means of a potentiometer located on the control box installed in the pump room. A 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.
In short: How to choose a water level management?
The main criteria for choosing a pool water levellers system is the size of the tank, whether or not you are permanently present and, above all, whether or not you want to get rid of a chore. Of course, the budget is also taken into account, but may seem derisory compared to the price of a pump and the price per m3 of water in some regions.
A simple flush float costs a few euros, electric floats a bit more, but a set of probes costs more than €500 ! So it’s up to you to see which system is best suited to your situation.
Part of our job is to advise you on the equipment best suited to your pool, but we have many other skills.