Does your Sprinkler look like the picture above?
Sprinkler heads can be victim to this sort of ongoing draining that seems to never stop. Whether you have a Pop up sprinkler or a rotor head. Each type can face this same problem. This issue is typically noticed on heads close to a sidewalk, patio or area where the draining water can be seen.
What you are experiencing is a head that is at the end of a lateral line in which the head is below the grade of the irrigation valve. When a sprinkler system is running, the valve opens the diaphragm and water passes through the valve and into the lateral lines which leads to each sprinkler head. When the irrigation valve is shut off, water is still in those lateral lines, however no continuous pressure is being applied and therefore sprinklers turn off. The water sits in the lateral line until the next time the valve opens and water passes through. When your sprinkler head continuous to leak it is due to gravity pulling that water to the lowest point and coming through the sprinkler head. Sprinkler heads that are below the grade of the valve, have gravity working on the water in the lateral line and is being forced to the lowest point. The water of course does not have enough pressure to push the head up and spray but it does have enough pressure to drain out of the head. No matter if you turn the irrigation valve off or manually close the flow control, it will not solve the issue because water is still in the lateral line.
The way to solve this problem is quite simpler than one might think. A check valve is needed to be installed on your sprinkler head. Depending on the type of sprinkler head you currently have installed you can either buy a check valve to install on the head. Or you would need to purchase a new irrigation head that has a check valve already installed. CLS typically purchases “SAM” heads (Seal-A-Matic) built by Rain bird that has these check valves installed. Check valves are available for both Pop Up spray heads and Rotor heads. Installing a check valve on your leaking sprinkler head will help solve your issue of running water.
P.S Be careful when you install your SAM head. Depending on how your lateral line is run, the head prior to the newly installed check valve could possibly start leaking. This happens because the SAM head of course has stopped leaking due to the check valve but the head prior is still downhill to the valve and is now the easiest exit point for water to exit via gravity. Be prepared to possibly have to buy multiple check valves/sprinkler heads in order to solve your problem