Estimate the location of the valves by picturing the layout of the sprinkler system. When you've narrowed down the possible location, careful probing can be used to find the exact spot. Use a long screwdriver to probe the ground by going down about 6 to 12 inches. Be careful when probing and go slowly so the probe doesn’t damage the sprinkler valve, water supply valve or the wiring.

Note the location of the pressure vacuum breaker or backflow preventer. The backflow preventer will likely be situated near the water source to the sprinkler system. Sometimes sprinkler valves are located close by. If not, the backflow preventer will still serve to provide a starting point for the path of the water lines to the sprinkler valves. If the path of the water line seems clear, try digging a little to follow the path to the sprinkler valve. Be careful not to break the water line when digging.

Find the sprinkler controller to serve as the starting point for the path of the wires for the sprinkler valves. Sometimes tracing the path of the wires can lead to the sprinkler valves. You may need to dig up some of the yard to follow the sprinkler wires. Take care not to damage the wires when digging.

The order in which the sprinklers in that zone start up can be another clue as to the location of the sprinkler valve. Have a helper manually turn on that zone at the controller and watch carefully. The sprinkler head that is closest to the valve should pressurize slightly before the rest of the sprinklers. Start at that sprinkler and try to find the valve nearby.

Notes:

If these methods don’t do the trick, you can buy or rent a solenoid activator or a valve locator. Renting these devices is the most economical option.

Consider drawing up a diagram of the sprinkler system once you have located the sprinkler valves to avoid this problem in the future.

It may be a while before you need to repair or replace a sprinkler valve again, and you may not recall the exact location by then.