Low Loss Header 40kW 1" Insulated with 4 x 1", Female Threaded TappingsLow Loss Header 40kW Low loss header separates boiler circuit from the heating circuit and is usually applied in medium or high power rating heating systems (practically, from 25 kW upwards), comprised of one or more boilers, particularly those with several heating circuits (e. g. underfloor heating + radiators + hot utility water). The application of a hydraulic unit brings many advantages.