Inside the water compartment, we house the essential climate and water system: Combi System: The Truma B4E Combi system handles both your hot air and hot water all in one unit. Frost Safety: This unit features a frost protection valve. As soon as the temperature drops below freezing, it will automatically dump the 10-liter storage tank of water to save the unit from being damaged. Accessibility: We've installed a Sure Flow 10-liter pump and a filter, ensuring everything is easily accessible. Pro