Precautions against frost
It is very important to protect your instantaneous water heater from frost. Water that is left in the heater and freezes will irrevocably damage the instantaneous water heater. Reparing the heat exchanger is costly and this damage is not covered by the warranty.
A the moment thre is chance that your instantaneous water heater could be exposed to frost you need to completely drain your instantaneous water heater. Disconnect the hose for incoming water and completely open the warm water tap (or shower head) at the lowest spot possible. Your instantanous water heater comes with a venting valve. This valve can be disconnected by hand. This enables air to flow into the system ensuring that all water will leave the appliance.
The venting valve is always located at the bottom of your instantaneous water heater and can easily be opened. The valve's appearance and location place can be differerent per model. Refer to your instantaneous water heater's instruction manual for more information.