The pressure withstanding capacity of the water heater depends on the tensile strength of the inner tank. The thicker its material, the more its tensile strength. Its outstanding pressure resistance performance extends the life of the tank and enhances its safe. All water heater are too be fitted with MFV ( Multi function Valve) which is supplied by the maker, set to pressure their tank can withstand. In case of water pressure reaching to its max, the MFV can are designed to release the excess water pressure through vent outlet provided. Always make such arrangement that these vent can release water in any of your drain. Never block these valve outlet.