Adjusting the flow rate on a plastic impact sprinkler involves manipulating the sprinkler's internal components. Here are the typical steps:

1. Locate the flow control adjustment mechanism:

   • This is usually a screw, knob, or dial located on the side or top of the sprinkler body.

2. Identify the direction of flow adjustment:

   • Typically, turning the adjustment mechanism clockwise will decrease the flow rate, while turning it counterclockwise will increase the flow rate.

3. Make adjustments in small increments:

   • Start by making small, gradual adjustments to the flow control mechanism.
   • Monitor the sprinkler's performance after each adjustment to see the effect on the spray pattern and coverage area.

4. Check the manufacturer's specifications:

   • Refer to the sprinkler's manual or technical specifications to understand the recommended flow rate range and adjustment guidelines.
   • This will help ensure you don't over-adjust the flow and damage the sprinkler.

5. Consider other factors:

   • The water pressure in your system can also affect the flow rate, plastic sprinkler so you may need to make additional adjustments if the pressure changes.
   • The nozzle size of the sprinkler may also impact the flow rate, so you may need to replace the nozzle if the flow is not within the desired range.

It's important to make flow rate adjustments gradually and monitor the sprinkler's performance to avoid issues like inadequate coverage or water wastage. With some experimentation, you can find the optimal flow rate for your specific irrigation needs.