Check valves keep your water flowing in one direction, automatically opening and closing a disc based on the amount of water pressure flowing through your irrigation pipes. The disc will open when the flow pressure is strong and close as the flow and pressure decrease.
Without a pre-installed or post-installed check valve, your sprinkler system will keep allowing water to drain, even after the sprinkler station is cut off, which wastes water.
Preventing excess drainage from your sprinkler system should be an important part of the decision-making process when configuring the design of your irrigation system. Pre-installed check valves within a sprinkler head have become the norm, however, there are some sprinkler systems that require post-installation within the sprinkler head or piping.