How can you use radiator pipes to communicate?

Radiator pipes can be used for communication by tapping rhythms or patterns on them, which can be picked up by others connected to the same piping system. This method relies on sound vibrations traveling through the metal pipes, allowing for messages to be conveyed over distances within a building. Different sequences of taps can represent different messages or signals, creating a simple and effective communication system. However, this method is limited to short distances and may not be easily understood without a pre-established code.