A slip joint shall be permitted on the inlet side of what plumbing fixture?

A slip joint is specifically designed to facilitate easy assembly and disassembly of plumbing connections, which is especially useful in plumbing systems. The inlet side of a trap is where a slip joint is particularly beneficial. This is due to the need for access to clean or replace the trap without requiring total disassembly of the plumbing. It allows for a flexible connection, accommodating slight misalignments or adjustments in the piping system.

In the case of fixtures like sinks, toilets, and showers, while various connections may be utilized, they often require a more rigid installation to maintain seal integrity, particularly for waste connections that are subject to frequent changes in pressure or flow. Therefore, using slip joints on these fixtures may not be as effective or advisable.

The trap, however, benefits from the versatility and ease of use that a slip joint provides, allowing plumbers to effectively manage drainage without compromising the functionality of the trap itself.