How Is the Water Pressure Harnessed on a Sprinkler?

Pop-up Sprinkler Heads

• Pop-up sprinkler heads are among the most common types of sprinklers in residential applications. These sprinklers are usually made out of plastic and use water pressure to lift a small supply tube inside the sprinkler body out of the ground. Once the water is turned on, it presses against the nozzle of the sprinkler and counteracts a small spring inside the tube. The water pressure continues to hold this tube up as water exits the nozzle. When the water is turned off, the pressure is released and the tube retracts into the body of the sprinkler.

Rotating Sprinkler Heads

• Rotating sprinkler heads are among the most complicated types of sprinklers available. That's because they contain a set of small internal gears. As water runs through the sprinkler body, it turns these gears and the head rotates in a circular pattern. Water is also used to lubricate these gears, so no oil or synthetic liquids should be used on the sprinkler. When water pressure is low due to nearby construction or municipal water testing, the heads may rotate more slowly.

Pressure Vacuum Breaker

• The pressure vacuum breaker is near the sprinkler manifold. This device prevents water from flowing from inside the sprinkler lines back into the main supply line. The breaker is a safety device that's required by code in most cities. As water flows through the breaker, it forces a spring and bonnet up. This allow water to flow in one direction only. When water pressure is low or reverses, the spring takes over and the flow of water is cut off. Low water pressure can also cause a breaker to leak from the top.

Valves

• Sprinkler valves hold water pressure back in a sprinkler system. These mechanical devices are triggered by an electric signal from the sprinkler timer. When the timer is in the off position, the valves are turned so that they block the flow of water to the supply pipes. When the timer is in the on position, the valves retract and allow the water to run to an individual zone. Water pressure does not continuously build when a valve is off. Instead, the water is held at the same pressure level as the rest of the main line, which is usually about 60 psi.