EBW™ brand anti syphon valves are recommended for all aboveground storage applications to prevent fuel from exiting the storage tank in the event of a broken line or leak. The anti syphon valve will shut off product flow when lines are broken, preventing fuel spillage and fire hazards. Each valve has an adjusting mechanism accommodating various liquid head pressure settings. Each valve also includes a pressure relief valve to eliminate thermal expansion of fluid in the lines. The adjusting mechanism is lockable after the preferred setting is made. Valves are set to maximum head pressure when shipped from the factory.