Attwood's exclusive Fuel Demand Valve ensures pressurized fuel does not reach the engine preventing engine flooding and fuel spillage. New EPA portable fuel tanks are required to remain sealed up to a minimum of 5psi. The Attwood Fuel Demand Valve prevents pressurized fuel from flooding the engine.. The valve provides fuel to the engine only when demanded by the engine during start up or engine operation. Designed in partnership with OEM engine manufacturers the Attwood Fuel Demand Valve is compatible with all OEM Engine brands and helps to ensure proper engine start up and function.