Different Valves Used in Water Distribution System

kennedy butterfly valve

butterfly valve throttle body

1″ butterfly valve

Values are an integral part of the water distribution system. These mechanical devices can change, direct, shut off, prevent backflow, and regulate water flow in pipelines. Each valve is uniquely designed to achieve different needs in the water distribution system. They can be made of stainless steel, brass, copper and several other materials. To learn more about them let’s have a look at six main valves used in the water distribution system:

1. Ball valves

Ball valves are the vastly used shut-off valves. They control water flow in pipelines through a rotational ball placed in the middle of the valve. This ball contains a hole through its centre that regulates the flow of water. When the ball’s hole is parallel to the water inlet, water can surge through the valve and escape into the pipes. When the hole is rotated 90° to the pipe through a handle, the passage is blocked, and water cannot flow through the valve. Rotating the handle by 1/4 turn is sufficient to seal off the flow of water.

Ball valves are common due to their reliability, speed, and durability. These valves are greatly used in residential and industrial applications to start and stop the water flow without a pressure drop. The ball produces a strong, watertight seal within the valve that prohibits leaking. Ball valves are also excellent for emergency applications where water flow needs to be blocked rapidly. However, these valves can only open and close water passages; they can not throttle the flow, as it risks destroying the seats or the ball.

The various designs of ball valves enable them to alter or deflect the water flow through multiple ports. The multi-port ball valves can divert water through as many as four different tracks. While most shut-off valves are only organized to control valves in a single direction.

2. Gate valves

The gate valves are also quite popular in the water distribution system. A wedge-shaped metal gate is installed that can be lowered to stop the water flow and raised to allow flow to resume. When the gate is fully raised, it retracts completely, allowing the water to flow through without any pressure drop. A wheel-shaped lever actuates gate valves on top of the valve. By rotating the lever, you can control the movement of the gate in the valve. These valves offer gradual restriction of flow, which avoids the water hammer. Water hammer results due to the sudden change in direction or stop, causing a banging sound within the pipe.

Like ball valves, gate valves only begin or halt the flow of water. Because using them for throttling applications will decrease their efficiency. Gate valves are good for straight-line flow, offering the least restrictions and diversions, like in big water supply lines.  Generally, gate valves are found in older plumbing systems because nowadays ball valves are more suitable due to their reliability. They can last longer if they are only used infrequently. For water supply systems where the flow of water needs to be turned on and off more frequently, a ball valve is preferred.

3. Globe valves

Globe valves are typically used to regulate water flow in pipelines. Unlike ball valves and gate valves, globe valves are suitably designed to start, stop, and throttle the flow of water. The spherical body of the globe valve homes a stationary ring seat. When the knob outside the valve is twisted, a disc-shaped device opens up a Z-shaped path and allows water to flow from one section into another. The knob can be opened and closed either completely to open and close the flow or partially to throttle the flow.

Globe valves provide a larger pressure drop than other shut-off valves. The curved Z-shaped passage inside the valve is more flow restrictive than ball valves and gate valves. So, they are ideal when managing water flow at lower pressures. But, since globe valves open and close gradually, they avoid water hammer.

4. Butterfly valves

The butterfly valve is another shut-off valve normally employed both to isolate and control water flow. There is a rotating disc present at the centre of a butterfly valve. This movable disc is controlled by the quarter-turn of a handle, like ball valves. When the handle is rotated, this disc bursts open, allowing water to pass through the valve. When the disc is closed, it forbids the movement of water. Butterfly valves fall into the “rotary motion” family of valves. This is because they control water discharge by operating a revolving mechanism that prompts the closure of flow.

A butterfly valve can be opened slowly to throttle water, though it is less useful than globe valves. Some designs of butterfly valves lock the disc partially open to maintain the throttled position. However, it is not instructed to use a butterfly valve to throttle flow for prolonged periods. Continual disclosure to rushing water will corrupt the disc and weaken the watertight seal.

Butterfly valves are lightweight, compact, and easy to operate manually. These properties make them ideal valves for regulating large volumes of water and gas. A high-pressure drop is certain with a butterfly valve. There is always resistance in the pipeline when the valve is open, which inflicts some limitations on where butterfly valves can be used.

5. Needle valves

Needle valves offer absolutely precise control of flow, unlike any other valve. They control water flow by lifting and lowering down a threaded, conical spindle. The sharp tip of the spindle sits perfectly on the valve seat at the bottom of the valve. A rotating stem actuates needle valves. As the stem is rotated, the spindle gradually rolls out of its valve seat, and water is incrementally allowed through the narrow path within the valve. Needle valves are used to isolate, regulate, and throttle water flow.

There is a controlled increase of flow with each twirl of the stem. This provides the operator with exact control over the flow of water. Needle valves have primary applications in systems where flow needs to be adjusted with great care to protect equipment. They are also ideal for operations where the flow needs to be shut off slowly or a very low flow rate is needed. Although the size of the water inlet and the internal spindle is small, needle valves are able of tolerating very high pressures.

6. Plug valves

A plug valve is a cylindrical valve that can be used for isolation or redirection purposes. There is a cone-shaped “plug” within the plug valve that has a hole in the center. When the lever is turned a quarter, the plug revolves to provide passage to the flow of water. The hole revolves flush to the valve walls when it is closed, and flow is blocked. Plug valves can also have multiple ports and be used to detract flow across multiple channels.

Plug valves can have either rectangular ports, diamond ports, or round ports. Round and rectangular ports are utilized for unimpeded water flow, whereas diamond ports impede flow. However, these valves can not be used to throttle flow. Plug valves are very simple in design. Moreover, their operation principle is similar to ball valves.