Under what condition should a clean-out fitting not be installed?

A clean-out fitting is an essential component in plumbing systems, designed to allow easy access for maintenance and cleaning of the drainage system. In selecting and installing these fittings, it is important to consider their ability to handle operational and maintenance stresses.

The correct condition under which a clean-out fitting should not be installed is when it cannot withstand the stresses of removal and re-installation. This is crucial because clean-outs are frequently used in plumbing systems for maintenance purposes. If a fitting is not durable enough to endure repeated removal, it can lead to leaks, damage to the surrounding plumbing, or even total failure over time. Therefore, ensuring that clean-out fittings are robust and durable is imperative for the reliability and longevity of a plumbing system.

While other choices may relate to various properties of clean-out fittings, they do not address the fundamental requirement for durability in repeated use. For instance, ensuring a gas-tight seal or the ability to withstand physical stresses is important, but if the fitting fails to hold up under stress from maintenance operations, it renders those features irrelevant. Likewise, whether the material is non-ferrous is a component of corrosion resistance, impacting longevity but not directly the ability to manage the stresses of being removed and replaced.