Irrigation systems are used to provide water to agricultural crops and residential landscapes. These systems often consist of irrigation controllers, solenoid valves, manual valves and a whole lot of piping.
To create an effective irrigation system, it helps to have a solid understanding of each of its components. Whether you’re an agricultural worker or just an eager gardener, learning about the different parts of an irrigation system can help you take better care of your crops or your garden and save water.
To start you off, we’re going to take a look at the typical valves used in irrigation systems. In this blog, we will focus on two major irrigation valve types: shut-off valves and control valves.
Shut-off valves are used to completely shut down the flow of fluid through an irrigation system. Shut-off valves can start and stop the flow of fluid but cannot regulate it. Because the valve needs to shut the entire line down, it’s best to install these valves as close to the water source as possible. This way, you can be sure that all parts of your irrigation system are completely shut-off.
Emergency shut-off valves can also be used if there’s a leak in the system. Once you see a leak, you can use the valve to stop the flow of fluid immediately. This way, you can mitigate the damage done by the leakage. In this situation, it’s important to have an irrigation controller that allows you to remotely close the valves.
- Gate valves
The gate valve is one of more commonly used shut-off valves. It uses a metal disk-shaped ‘gate’ to block the flow of fluid. This disk is vertically attached to the stem, which in turn, sits on top of the valve body. This stem can be rotated more than 360 degrees to raise or lower the disk accordingly. When the disk is lowered, it blocks the flow, closing the valve. When it’s raised, the flow resumes.
When fully open, gate valves offer little resistance to flow. Because of this, gate valves are typically used as an inline valve. Inline valves are designed to simply allow the fluid to pass through completely with low pressure drop. Such valves are installed underground and inside a valve box. This protects it from extreme temperatures.
Gate valves, however, cannot regulate the flow of fluid. This is because the size of the valve opening is disproportionate to the amount of fluid flowing through it. If you were to open a gate valve half-way, there will be an excessive amount of high-velocity fluid flowing through a small gap. This will wear down the disk faster than usual.
- Ball valves
Instead of a disk, ball valves use a metal or PVC sphere to control the flow of fluid. A hole is bored through the centre of this sphere, corresponding with the size of the inlet and outlet. When aligned with the inlet and outlet, this hole allows the fluid to flow through. However, when the sphere is turned 90 degrees via the stem, the closed sides of the sphere block the flow.
Since ball valves only require a 90 degree turn to open and close, they are considered fast-acting valves. Fast acting valves are useful if you need to shut-off your irrigation system quickly.
On the other hand, shutting off a valve too fast can also cause ‘water hammer’, a hydraulic shock that occurs when a valve is shut-off abruptly. It creates pressure waves at the closed end and sends them back through the pipes. This can cause ruptures and vibrations in the system.
Control valves are used to open, close and regulate your irrigation system. What makes control valves different from shut-off valves is their ability to manage the flow rate.
Most control valves are linearly actuated. This means that the amount of fluid flowing through the valve body is proportional to the opening created by the disk. Because of this, you can safely control the flow rate without having to be concerned about damaging your disk.
- Globe valves
Globe valves get their name from their body shape. However, since globe valves have different flow types, it doesn’t always have a globe shape.
The four main flow types include straight-flow, angle-flow, cross-flow and y-flow. These flow types are unidirectional. This means you cannot reverse the flow of fluid as it can put too much pressure on the stem and the disc.
Globe valves use a horizontal disc to start and stop the flow of fluid. Unlike gate valves, however, the globe valve disk comes into contact with seating at a right angle. This allows a tighter seal when the valve is closed and thus reduces leakage.
- Anti-siphon valve
Anti-siphon valves have a backflow preventer that stops irrigation water from siphoning back into your clean water supply. It does this through a variety of ways, but a common method is through use of air vents.
The siphoning effect is only possible when a pipe or tube is completely filled with fluid. However, if you were to introduce air into the pipes, it disrupts any siphoning that could occur. Thus, opening vents and letting air into the pipes prevents contaminated water from mixing with your clean water supply.
Most building codes require properties to have an anti-siphon valve. Unlike inline valves, anti-siphon valves need to be installed at least 15cm above ground.
These are the typical valves that you might see in your everyday irrigation system. Before you have a major failure with your irrigation valve, check signs for repair and maintenance Irrigation System.Using them incorrectly can cause damage to your irrigation system and your property. As such, it’s important to understand the function of each of these valves.