After screwing the fitting hand tight on the pipe, what should you immediately do?

The appropriate course of action after securing a fitting hand tight on the pipe is to select a pipe wrench size. This step is critical because, while a hand-tight connection may initially seem secure, it is not sufficient for ensuring a leak-proof seal in most plumbing and piping applications.

Selecting the appropriate size of pipe wrench ensures that you can adequately tighten the fitting to the required specifications. Using the correct tool helps in applying the necessary torque to achieve a secure connection, which is essential for preventing leaks. It is especially important in applications where the joint will be subject to pressure or movement, as an inadequate connection could lead to system failure or leakage.

The other options, while they may seem relevant in the context of working with pipe fittings, do not immediately follow the action of securing the fitting hand tight. Checking for leaks should be performed after the fitting has been properly tightened, marking the position is typically used to ensure alignment before tightening, and applying heat is not a standard procedure in this context and could damage the fitting or pipe material. Therefore, the focus should be on selecting the right tools to ensure proper installation and safety.