What type of tap is typically installed externally and includes a hose union connector?

The type of tap that is typically installed externally and includes a hose union connector is indeed the bib tap. Bib taps are designed primarily for outdoor use, often found in gardens or on building exteriors. They allow for the easy attachment of hoses for watering plants or washing vehicles, which is facilitated by the hose union connector. This connector creates a secure and watertight connection with standard hose fittings, making it practical for external applications.

In contrast, other types of taps mentioned serve different purposes and environments. Faucets are generally found indoors, such as in kitchens or bathrooms, and do not typically feature a hose union. Pressure-relief taps are specialized for safety in systems that need to relieve excess pressure and are not meant for general use like a bib tap. Bath taps are designed specifically for filling bathtubs and include features that cater to indoor plumbing rather than external connections. Thus, the bib tap is uniquely suited for outdoor installations where hose attachment is required.