The WaterPORT 4.0 Gallon Fill Regulator Valve (WX1120) comes standard with every WaterPORT 4 Gallon Pressurized Water Tank (SC1000) Kit and WaterPORT 8 Gallon Pressurized Water Tank (WK1000) and is required to safely fill and pressurize your tank from a garden hose.
The WaterPORT Day Tank Fill Regulator Valve (WX1120) is already included with the WaterPORT 8 Gallon Pressurized Water Tank (WK1000) and the WaterPORT 4.0 Gallon Fill Regulator Valve (WX1120) base kit, so you would only order it if you needed a spare or a replacement.