Irrigation valves, operated by an irrigation controller, are the physical control centre of an automatic irrigation system. So for an irrigation system to function effectively, and for your garden to stay green and healthy, it’s vital that they’re in constant working order. So in the event that something something does go wrong, we’re here to help you understand what’s inside the valve so should you need to open one up, you’ll know what you’re looking at.
Valve Body Types
The first thing to note, is that there are typically two distinct types of irrigation valve bodies: Screw Top & Jar Top.
The inside of each valve body type functions exactly the same. But it’s the composition of the outside, and how you open up the unit that differs. A Screw Top Valve is disassembled by undoing a set of screws (don’t lose any) to remove the ‘top’, and a Jar Top Valve is disassembled by unscrewing a collar that surrounds the valve body (like how you would unscrew a lid off a jar).
Once you’ve unscrewed the valve apart you’ll notice you’ll be left with 3 distinct parts: The top, the inside & the base.
The base of an irrigation valve
Starting at the base, because it’s the simplest. When servicing, this is a single fixed part that will remain in-line. Given there are no moving parts in a valve bottom, they rarely fail, unless something external causes them to split & leak (like a stray ball, or tree root).
The inside of an irrigation valve
The inside of an irrigation valve is where we start look at the active parts of the valve, it typically consists of 2 moving parts: A diaphragm & a spring. The diaphragm is the physical gate that controls the flow of water. When the valve is closed the rubber seal becomes water-tight and stops water from flowing through. Often when a valve failing to shut off, it’s because debris has managed to find it’s way into the valve & is not allowing that diaphragm to create a complete seal. The debris could be a stone, or fine grit, and a repair can simply be giving it a clean. But the in case or a split or permanent damage, replacement of the diaphragm is required.
The top of an irrigation valve
And finally the top is what controls the movement of that diaphragm, commonly you’ll find a bleed mechanism, a solenoid coil & a flow control (optional feature).
The bleed mechanism can be a small screw, or lever that can manually open the valve by breaking the pressure seal inside the valve, allowing the diaphragm to unseal & allow the flow of water. The solenoid coil does the same buy is activated automatically by an irrigation controller. A flow control, which can be found on many (but not all) valves can be adjusted to reduce or increase the flow of water through the valve.
If you find a valve isn’t coming on, it’s often something related to the top of the valve & specifically the solenoid coil. Common reasons for failure are electrical, eg: the irrigation cable is damaged, the controller isn’t delivering power to the coil, or the coil has simply failed.
