State where the following types of pipes are used: Black mild steel.

Black mild steel pipes are commonly used in plumbing and heating systems, as well as in the construction of gas and oil pipelines. They are also used in industrial applications such as in the transportation of water, steam, and other fluids.

Black mild steel pipes are typically used in low-pressure, non-corrosive applications, such as:

- Low-pressure water distribution systems
- Natural gas distribution lines
- Irrigation systems
- Oil and gas pipelines in non-hazardous environments
- Structural supports and frames in non-critical areas
- Sewerage and drainage systems