What is the minimum size that overflow pipes must be in relation to supply pipes?

The minimum size that overflow pipes must be in relation to supply pipes is that they should be larger than the supply pipe. This design requirement ensures that in the event of an overflow or excessive flow situation, the overflow pipe can effectively handle the additional volume without causing back pressure that could damage the system or create a hazard. A larger overflow pipe allows for a greater capacity to divert excess fluid safely and prevents potential flooding or spillage that could occur if the overflow pipe were of the same size or smaller than the supply pipe. This principle is critical for maintaining a safe and reliable oil burner operation, as it mitigates risks associated with overfilling or pressure build-up in the system.

The choice of having a smaller or the same size pipe would not provide the adequate drainage capacity needed in an emergency, leading to potential safety issues. Therefore, ensuring that the overflow pipe is larger than the supply pipe is essential for effective system management and safety compliance.