The HYDROKNOT is a small value installed at the "T" just before the riser or sprinkler in an irrigation system. Should the riser or sprinkler crack or break, the water is shut off just to that sprinkler while all the other sprinklers continue to operate. It stops the often seen "geyser" that occurs along with the wasted water (up to 120 gallons a cycle) when a sprinkler or riser is damaged or broken. Since it is below ground it's a one time purchase and is guaranteed for 10 years. This is a great way to conserve water and still allows for watering plants and lawns without the worry of wasting water if a sprinkler is damaged or broken. It can be used in any position so it's great for drip irrigation as well as traditional sprinkler set ups. Each time the system shuts off the value resets itself, if the sprinkler has be fixed the system will operate as normal, if not the system will shut off just that sprinkler until it is repaired.