How should pipe threads be sealed during installation?

When sealing pipe threads during installation, the most reliable method involves the use of Teflon tape or pipe dope. Teflon tape, also known as PTFE tape, is specifically designed for creating a watertight seal on threaded pipe connections. It is chemically resistant and lubricates the threads, allowing for a tighter fit when the pipes are joined.

Pipe dope, or thread sealant compound, serves a similar purpose by filling any gaps between the threads and preventing leaks. It is often used in situations where the tape may not be effective or where a more robust seal is needed.

Using duct tape is not appropriate for this application, as it is not designed for high-pressure systems and can degrade over time, leading to leaks. Silicone sealant is also unsuitable, as it does not bond well with metal and can also break down under high pressures or temperatures. Epoxy resin typically bonds permanently, which is not advisable for threaded connections intended to be disassembled in the future.

Thus, Teflon tape or pipe dope stands out as the correct choice for sealing pipe threads, ensuring durability and reliability in irrigation systems.