on the early vailant 824 the filling loop is internal and is situated under the right hand side of the boiler, there is usuly an L shaped key, if the key is not available. remove the grill under the boiler you will see a round hole in the brass fitting where the cold water goes in to the boiler, inside you will see the slot that the key will fit in. if you dont have the key use a stubby flat blade screw driver open the valve slowly and alow water in to the boiler untill the pressure is correct and then switch it off again. done
Mark, February 2007