The filling loop is a part that only occurs on systems 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 external or internal, 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 disconnects the filling loop once it has been removed. Includes O-ring and Washers

Brand Name	Ideal Heating