Highly reliable anti-freeze electric high-tech heating cartridge, completely rustproof, made of specially treated stainless steel with brass nut and seal, with dry-run and overheating protection. Protects more than 40 litres of water from freezing at outside temperatures down to -25°C. For simple installation in all fresh and waste water tanks. If the water temperature drops to approx. 5°C, the frost monitor starts to heat the water. When the water has reached a temperature of 10°C, it stops heating.