Answer
Aug 20, 2025 - 09:55 AM
No, you do not simply divide the available PSI (pounds per square inch) by the number of heads in a zone to determine the pressure at each sprinkler head.
Here's why and what you should consider:
Here's why and what you should consider:
- Pressure Loss: As water flows through the pipes, fittings, and valves of an irrigation system, it encounters friction, which causes pressure to drop. This phenomenon is called friction loss.
- Dynamic Pressure: The available 80 PSI is likely your static pressure – the pressure when no water is flowing. When water flows and the sprinkler heads are operating (dynamic pressure), the actual pressure at each head will be lower than the static pressure due to friction loss and the water demand of all the heads operating simultaneously.
- Head-Specific Performance: Each type of sprinkler head (spray, rotor, drip, etc.) is designed to operate optimally within a specific PSI range. If the pressure is too high, it can lead to misting, reduced efficiency, and potentially damage the heads. If the pressure is too low, the heads may not pop up or cover the intended area.
- Water Flow Rate (GPM): This is the amount of water available at your source, measured in gallons per minute (GPM). You can measure this using a five-gallon bucket and a stopwatch.
- Sprinkler Head Requirements: Each sprinkler head has a specific GPM requirement at a specific operating pressure to achieve its stated coverage radius. This information is typically found on the manufacturer's performance charts.
- Friction Loss: Calculate the pressure loss due to friction in the pipes, fittings, and valves within the zone. You can find friction loss tables online or use calculators to estimate this.
- Number of Heads per Zone: The number of heads you can realistically put on a zone depends on your available flow rate and the GPM requirements of the selected sprinkler heads. Divide your available GPM by the GPM required by each head to determine the maximum number of heads that can operate effectively on that zone.
- Pressure Regulation: If your available PSI is significantly higher than the optimal operating pressure for your chosen heads, you may need to install pressure regulators to reduce the pressure and prevent problems like misting or equipment damage.
