Which hydrant type features no main valve while having separate valves for each nozzle?

The correct answer is that a wet-barrel hydrant features separate valves for each nozzle and does not have a main valve. In a wet-barrel hydrant, the valve mechanism is located directly at each nozzle, allowing for immediate access to water without needing to open a main valve like in a dry-barrel hydrant. This configuration is particularly advantageous in areas where the hydrant does not need to be drained in colder temperatures, as the water is always kept within the barrel.

In contrast, a dry-barrel hydrant is designed for colder climates and includes a main valve that is located below the frost line. This type of hydrant prevents water from being stored in the barrel, reducing the risk of freezing. Flush hydrants, on the other hand, are generally used where water is not needed for firefighting purposes, mainly for flushing out sewers or drains. Standpipes are systems designed to carry water to various sources, typically within buildings or for firefighting operations, but they do not fall into the same category as hydrants when discussing nozzle valve types.

Thus, the unique feature of the wet-barrel hydrant—having separate valves for each nozzle without a main valve—is what makes it the correct answer.