What sort of shut-off valve should be used between two buildings?

Using a full-way valve between two buildings is ideal because it allows for a complete, unobstructed flow of fluid when it is fully open. This type of valve is designed for the purpose of isolation and can effectively handle larger diameters, making it suitable for applications that may involve significant volumes of water or other fluids.

A full-way valve also ensures that if maintenance is required on either building's plumbing system, the flow can be completely shut off without any leaks or difficulties, which is crucial for safety and efficiency. Additionally, the design of a full-way valve allows it to withstand higher pressures, which might be present in inter-building plumbing setups.

In contrast, while other types of valves like bypass or gate valves might function for specific situations, they may not offer the same level of reliability and capability for isolation as a full-way valve. Therefore, the recommendation for a full-way valve emphasizes a focus on safety, flow capacity, and the ability to effectively isolate one section of a plumbing system from another.