The principle of pressurised water heating systems with tank on the roof

The vacuum tubes are connected to the tank and installed on the roof. The water reaches the end point under pressure. The system can provide hot water for home use 12 months per year (up to boiling temperature in summer and around 45-55°C) for more than 20 years. The system is designed to work at temperatures as low as up to -30°C. Is not suitable for pool heating. Unlike the non-pressurised systems the pressurised ones are being reloaded with cold water during usage which makes the hot water in the tank get cooler when hot water is used.