What does a bubble at a connection indicate?

A bubble at a connection indicates that there may be a problem with the connection because it suggests the presence of a gas leak. When gas escapes from a connection, it can create bubbles in a soap solution that is often used to detect leaks. This is a critical safety concern, as leaks can lead to hazardous situations. Observing bubbles signifies that the joint is not sealed properly and requires immediate attention. Ensuring a secure and leak-free connection is essential for safe operation when using LPG or CNG in engine fuel systems.