How to Replace a Sprinkler System Valve and Solenoid

The in-ground sprinkler system that irrigates your lawn and garden has different types of valves that control the flow of water. Some of these sprinkler valves are above ground, and others are usually located in recessed in-ground boxes. Sooner or later, it's likely that you'll face a sprinkler valve replacement or replacement of a solenoid that controls a valve. Though this project requires some plumbing skills, it's a fairly simple DIY project you can tackle in a weekend.

A typical lawn irrigation/sprinkler system has three different types of valves controlling the flow of water:

• A main shutoff valve controls water flow to the entire sprinkler system. This valve allows the sprinkler system to be shut down without interrupting water flow to the rest of the home. Because this valve sees infrequent use, it doesn't fail very often, and most homeowners will never need to service it.
  
  
• A stand-alone anti-siphon valve is included when the sprinkler zones are controlled by below-ground in-line valves, which by their design cannot have anti-siphon capability. The stand-alone anti-siphon is a vacuum-breaker device that is sometimes integrated with the main shutoff valve or is part of the backflow preventer assembly. It's also rare for this valve to require repair or replacement.

There is a third type of valve that most homeowners will need to service or replace at some point — the zone valves, which feed sprinkler heads in different areas of the yard. There are two different types of zone valves you may encounter:

• An in-line zone valve is installed below ground, usually grouped with the other valves in a recessed box set into the ground. Each of these valves will have a wired device known as a solenoid attached to it. The solenoid receives low-voltage signals from the timer/controller unit, causing the sprinkler zones to activate according to the programmed schedule.
  
  
• An anti-siphon zone valve is an above-ground zone valve. It operates in exactly the same way as an in-line zone valve but is shaped slightly differently and has a built-in anti-siphon mechanism that eliminates the need for a stand-alone anti-siphon valve.

When a valve stops working correctly, it's possible that the problem lies with the solenoid rather than the valve itself. Thus, it's always a good idea to consider replacing the solenoid before turning to full replacement of the valve, which is a bit more involved. This is quite easy to do:

1. Make sure low-voltage current to the solenoid is turned off at the controller. You can simply unplug the controller itself if necessary.
   
   
2. Disconnect the controller wires from the solenoid attached to the zone valve. This is usually just a matter of unscrewing wire nut connectors.
   
   
3. Unscrew the solenoid from the valve housing. Generally, this is done by unscrewing it in a counterclockwise direction.
   
   
4. Check for any debris clogging the port where the solenoid sits. Wipe away this debris and rinse off the solenoid itself.
   
   
5. Check the O-ring on the solenoid for debris or wear and replace the O-ring if necessary. Reattach the solenoid, reattach the wires and see if this simple service returns the valve to good operating condition.
   
   
6. If the valve still doesn't work correctly, replace the solenoid with an identical replacement. Then, reattach the low-voltage controller wires and test the operation of the system. If the zone still does not operate correctly, then replacement of the entire valve unit is the next step.

Some zone valves are designed so the inner diaphragms that control the water flow can be cleaned and replaced:

1. Shut off the controller and turn off the water supply to the sprinkler system.
   
   
2. Disconnect and remove the solenoid.
   
   
3. Remove the bonnet screws that secure the cap on the zone valve. Lift off the cap to expose the spring and rubber diaphragm inside. (Some valves have a screw-on cap that is removed by twisting it counterclockwise.) Remove the spring and set it aside.
   
   
4. Remove and inspect the rubber diaphragm. Clean away any debris. If the diaphragm seems cracked or brittle, replace it with a new one.
   
   
5. Reassemble the valve, making sure to reinsert the spring. Reattach the solenoid and then turn the system back on and test the operation.

In-line zone valves are usually found inside a recessed ground box. In some cases, most or all of the valves may be buried in soil with only the tops and the controller wires exposed. In this case, you'll need to remove plenty of soil to go forward with sprinkler valve replacement.

An in-line zone valve can be attached to the PVC sprinkler pipes in a number of ways, but in the most common scenario, it will be fitted with threaded male adapters that are solvent-glued to the sprinkler pipes. Removing the old valve usually means cutting through the sprinkler pipe on one side of the valve in order to unscrew it from the adapter on the other side. Be prepared to be flexible, as your configuration might look different. Also be aware, that replacing a valve is a job that requires some experience working with pipes.

Anti-siphon zone valves are the above-ground style of zone valve. They are designed with a vacuum-breaking anti-siphon feature built into them. These valves extend up and out of the ground and are usually grouped together near the system's main shutoff valve.

The procedure for replacing an anti-siphon zone valve is similar to replacing an in-line valve, but it is even easier because you have open access. In this instance, use grip-fit adapters rather than solvent-glue adapters since these adapters can be used with any pipe material.