The vented sealed central heating system is an increasingly popular type of central heating system because of its simplified design. The system is fed and pressurised with water direct from the mains, then sealed. This eliminates the need for the system water feed tank and open vent pipework in the loft, which therefore simplifies and reduces the cost of the installation process and reduces maintenance requirements. In the diagram on the right, a conventional tank-fed indirect hot water cylinder has been used with its own header tank in the loft.