How is a valve described if it is completely leak-tight?

A valve that is described as completely leak-tight is referred to as resilient. This term indicates that the valve is designed to maintain a complete seal, preventing any fluid from leaking through its closure mechanism under the pressure conditions it is subjected to. In the context of water distribution, a resilient valve is critical as it ensures the integrity of the system by preventing leaks, which can lead to water loss, pressure drops, and potential damage to the infrastructure.

While other terms such as substantial, durable, or effective may relate to different aspects of a valve's performance or construction, they do not specifically capture the essence of a valve's ability to maintain a stringent seal against leaks. Durability might suggest a long-lasting nature, effectiveness could refer to general performance, and substantial may imply strength, but none specifically denote the leak-tight characteristic that "resilient" conveys.