For installations with Spring panels: in order to check the watertightness of the system without wasting heat transfer fluid, we recommend that you fill the circuit with water, then make sure that no leakage is observed along the solar circuit. If, however, you notice a loss of pressure in the system, there is definitely a leak somewhere.
Once the circuit is watertight, remember to drain the water before filling it with antifreeze. If antifreeze and water mix inside the circuit, this would conversely increase the freezing point of the mixture. Always check the final freezing point with a refractometer to see if it is acceptable for the geographical area of the installation. If it is too high, more antifreeze must be added.