Compared to cast iron pipe fittings, BS (British Standard) standard malleable iron fittings typically have several advantages in terms of their weight:

1. Lighter Weight:
   Malleable iron fittings are generally lighter in weight than their cast iron counterparts, often by a significant margin. This is due to the manufacturing process and the material properties of malleable iron.

2. Easier Handling and Installation:
   The reduced weight of malleable iron fittings makes them easier to handle and install, requiring less physical effort and reducing the risk of injuries or strains for the workers involved.

3. Lower Transportation Costs:
   The lighter weight of malleable iron fittings translates to lower transportation costs when moving the fittings from the manufacturing facility to the job site. This can result in overall cost savings for the project.

4. Improved Ergonomics:
   The lighter weight of malleable iron fittings improves the ergonomics of the installation process, reducing the physical strain on the workers and potentially increasing productivity.

5. Suitability for Overhead Applications:
   The reduced weight of malleable iron fittings makes them more suitable for overhead or suspended piping applications,  BS Standard Malleable Iron Fittings  where the weight of the fittings is a critical factor in the overall system design and support requirements.

6. Enhanced Safety:
   The lighter weight of malleable iron fittings reduces the risk of dropped or falling objects during handling and installation, improving overall site safety.

It's important to note that while malleable iron fittings are generally lighter than cast iron, the specific weight difference can vary depending on the size and configuration of the fittings. Additionally, the improved weight characteristics of malleable iron fittings must be balanced against other factors, such as cost and availability, to determine the most suitable option for a particular project or application.