Threaded cast-iron drainage fittings should not be used in which type of system?

Threaded cast-iron drainage fittings are specifically designed for use within drainage systems, where their robust construction can effectively handle the pressures and flow conditions present in such applications. When considering the appropriate context for their use, it becomes clear that they are not suitable for water systems.

Water systems typically involve pressurized water supply lines, where the fittings need to ensure a watertight seal under pressure. The risk of leakage and the potential for corrosion or failure in pressurized conditions make threaded cast-iron fittings a poor choice in this scenario. Instead, materials and fittings specifically designed to withstand the demands of high-pressure environments, such as copper, polyethylene, or various plastic fittings, are preferred for water systems.

In contrast, threaded cast-iron fittings are well-suited for drainage systems, soil systems, and ventilation systems, where lower pressures and different fluid dynamics are at play. Their use in these areas allows for durability and reliability where needed. Therefore, the assertion that threaded cast-iron drainage fittings should not be used in water systems is grounded in the distinct requirements and challenges presented by pressurized water supply lines.