The filling loop is a part that only occurs on boilers that deal with central heating. The filling loop allows the user to manually modify the amount of water in the central heating system if the pressure has decreased. Filling loops can be internal or external, depending on the type of appliance you have. If the filling loop is external to the appliance it is usually removable due to water regulations. However, if the loop is internal, there is usually a key that can be removed to disconnect the filling loop after use. Comes with O-rings and Screws

Brand Name	Worcester Bosch