Inline valves are an important part of any irrigation system. They’re the link between the controller and the sprinklers, and they control when water flows into a zone. They can be arranged either singly throughout the system, or located together.
Single inline valves are separately placed to control the flow of water through lateral pipes for a specific zone. Each valve is connected to the main line, with the lateral pipes located downstream from it. The buried valve should be covered with a valve box to protect it from dirt, the elements, vandalism, and damage due to mowers and other equipment.
The single valves, along with the lateral pipes, can be laid out in different configurations for optimum sprinkler performance. For example, the straight line lateral circuit, with the valve located at the very end of the line, is the least optimum layout. Much better is a split-length lateral circuit route with the valve located in the center of the sprinkler line. This arrangement reduces the required pipe size, and balances pressure losses throughout the circuit.
A second method of setting up inline valves is to group them together in a manifold. An irrigation manifold is a pipe that branches into a number of openings, and each opening is used to attach a single valve that controls one zone.
The downside of manifolds is that if one of the valves starts to leak at the inlet, you have to replace not just the faulty valve but all of the valves, even the ones that are operating properly.
You can purchase pre-made manifolds in many different sizes (e.g. 2-6 valves), depending on how many valves and zones are needed. Homeowners can also design and assemble their own manifolds, basically using pvc (polyvinyl chloride) pipe, tees, and elbows. Sometimes a number of manifolds are joined together with pvc pipe to keep them all in one location.
It’s recommended that you place valve manifold assemblies near the zones they’re serving (e.g. front and backyard), and in an accessible spot for maintenance. Grouped valves should also be protected by a valve box, and not buried directly in the ground. Don’t locate them near stairwells, utilities, window wells, or in areas that slope downward to the house. You also don’t want them in the middle of play areas or where they interfere with walking.
How Valves Work
The kind of valves usually found in automatic irrigation systems are called solenoid valves. They consist of the solenoid (black cylinder with wires), which is wired directly to the controller, and the valve itself. When the controller sends a signal to the solenoid, it either opens or closes the valve. Arrows on both sides of the valve show the correct flow direction when hooked up to the water supply.
For single valves, the inlet side connects to the main line. The inlet is under constant pressure, and only lets water pass through when opened by the controller. The outlet side of the valve connects to the lateral lines that carry water to the sprinklers. Lateral lines are only under pressure when the water is passing through an open valve.
With grouped valves, one side of the manifold is connected to the main line, and the other side can be connected to piping that continues to other manifolds, be capped off, or be used to install an automatic drain. The inlet side of each valve connects to the manifold, and is under continual pressure from the main line so that water can flow when the valve is opened. The outlet valve side connects to lateral pipes running to a specific zone.
Advantages of Single Valves
- Smaller valve boxes are less obtrusive in the landscape.
- Less lateral pipe is needed, which reduces pressure loss due to friction and allows optimum hydraulic locations in system.
- Easy to repair or replace the valve in the working space.
Disadvantages of Single Valves
- Usually longer runs of wire to reach all the valves.
- Smaller valve boxes can get hidden under turf and can be difficult to locate for maintenance or repair.
- Longer runs of main line pipe, which is more expensive.
- Wires can be difficult to find to repair unless you know where the pipes run (wires are usually buried in the pipe trench).
Advantages of Manifolds
- Shorter runs of wire from controller to manifold locations.
- Larger valve boxes can be easier to locate, and some homeowners place them outside the landscaped area.
- Usually shorter runs of more expensive main line pipe.
Disadvantages of Manifolds
- Longer runs of lateral pipes.
- Manifolds can be very difficult to work with and some irrigators don’t recommend manifold valves for the following reasons:
- If one of the valves starts leaking on the inlet or outlet side you have to cut out non-leaking valves to get to the one that needs repair or replacement because of the reduced working space.
- Often the entire manifold has to be replaced due to a simple pvc leak when the valves are piped too close together. What would have been a simple job is going to cost much more.
- Some manifolds are built too close to the tee in the main line so there isn’t much pipe to work with when doing repairs.
- Even if manifolds are built with enough room to work on the valves or pipes, it’s still a more difficult task due to the tight configuration.
Call the experts at South Austin Irrigation at (512) 534-7449 or fill out our Service Request form for professional maintenance and repair to your sprinkler system.