What type of valve has a flexible piece that can be adjusted to control water flow?

The diaphragm valve is designed with a flexible diaphragm that can be adjusted to regulate the flow of water. This diaphragm, typically made from rubber or similar materials, moves up and down in response to changes in pressure or operator adjustments, allowing for precise control over the flow rate. This functionality makes diaphragm valves particularly effective for controlling flow in applications where precise regulation is vital, such as in water distribution systems.

In contrast, a gate valve operates by lifting a gate out of the flow path, while a ball valve uses a spherical disc to block or allow flow. Butterfly valves involve a rotating disc to manage flow but do not have the same flexible component that allows for gradual adjustment like the diaphragm valve does. Each of these other types of valves serves its own purpose, but they lack the unique ability to fine-tune flow rates with a flexible piece as exhibited by diaphragm valves.